Wavelength multiplexer/demultiplexer using metamaterials for optical fiber communications

ABSTRACT

Systems, devices, and techniques for performing wavelength division multiplexing or demultiplexing using one or more metamaterials in an optical communications systems are described. An optical device may be configured to shift one or more phase profiles of an optical signal using one or more stages of metamaterials to multiplex or demultiplex wavelengths of optical signals. The optical device may be an example of a stacked design with two or more stages of metamaterials stacked on top of one another. The optical device may be an example of a folded design that reflects optical signals between different stages of metamaterials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 ofU.S. Provisional Ser. No. 62/968,531 filed on Jan. 31, 2020, the contentof which is relied upon and incorporated herein by reference in itsentirety.

BACKGROUND

The following relates generally to one or more optical communicationsystems and more specifically to a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communications.

Optical communications systems are widely deployed to provide varioustypes of communication content such as voice content, video content,packet data, messaging, broadcast content, and so on. Opticalcommunication systems rely on various types of adjusting of opticalsignals onto a common transmission optical fiber to increase the amountof information that can be transmitted over the transmission opticalfiber.

SUMMARY

The systems, methods, and devices of this disclosure each have severalnew and innovative aspects. This summary provides some examples of thesenew and innovative aspects, but the disclosure may include new andinnovative aspects not included in this summary.

An apparatus may include a first substrate that is opticallytransmissive, a first stage of metamaterials positioned in proximity toor in contact with the first substrate, a second stage of metamaterialspositioned in proximity to or in contact with the first substrate, areflector positioned opposite the first substrate and configured toreflect an optical signal that passes through the first stage ofmetamaterials to pass through the first stage of metamaterials again,and where the first stage of metamaterials and the second stage ofmetamaterials are configured to multiplex a first optical signal havinga first wavelength and a second optical signal having a secondwavelength into a third optical signal having the first wavelength andthe second wavelength based on shifting a first phase profile of thefirst optical signal and a second phase profile of the second opticalsignal by the first stage of metamaterials and the second stage ofmetamaterials.

In some examples, the first stage of metamaterials may be configured toshift the first phase profile of the first optical signal and the secondphase profile of the second optical signal and output a first shiftedoptical signal and a second shifted optical signal, and the second stageof metamaterials may be configured to shift a third phase profile of thefirst shifted optical signal and a fourth phase profile of the secondshifted optical signal and output the third optical signal that includesthe first wavelength and the second wavelength.

Some examples of the apparatus may include cladding positioned betweenthe first stage of metamaterials and the reflector, the cladding havinga thickness configured to mitigate losses of optical signals interactingwith the first stage of metamaterials, or to protect the first stage ofmetamaterials, or a combination thereof.

In some examples, the thickness of the cladding may be between 500nanometers and 2 micrometers.

Some examples of the apparatus may include a first reflector and asecond reflector configured to reflect the first optical signal and thesecond optical signal, the first substrate positioned between the firstreflector and the second reflector.

In some examples, the first stage of metamaterials and the second stageof metamaterials may be positioned in proximity to or in contact withthe first reflector.

In some examples, the first stage of metamaterials may be positioned inproximity to or in contact with the first reflector, and the secondstage of metamaterials may be positioned in proximity to or in contactwith the second reflector.

In some examples, the first reflector forms a first aperture forreceiving the first optical signal and the second optical signal, andthe second reflector forms a second aperture for outputting the thirdoptical signal.

In some examples, the first reflector forms a first aperture forreceiving the first optical signal and the second optical signal andforms a second aperture for outputting the third optical signal.

In some examples, the first substrate, the first reflector, the secondreflector, the first stage of metamaterials, and the second stage ofmaterials form a Fabry-Perot cavity configured to generate one or moreresonant reflections of the first optical signal and the second opticalsignal.

In some examples, the first stage of metamaterials may includeoperations, features, means, or instructions for a set of metamaterialstructures arranged in a pattern to shift a phase profile of the opticalsignal based on one or more parameters of each metamaterial structure ofthe set of metamaterial structures.

In some examples, the one or more parameters of the metamaterialstructure includes a height of the metamaterial structure, across-sectional profile of the metamaterial structure, a diameter of themetamaterial structure, a dielectric property of the metamaterialstructure, or a combination thereof, and where at least one of the oneor more parameters of the metamaterial structure may be different for afirst metamaterials structure compared to a second metamaterialstructure.

In some examples, a total phase shifting caused by the first stage ofmetamaterials may be based on a phase shifting profile of eachmetamaterial structure and the pattern of the set of metamaterialstructures.

An apparatus may include a substrate that is optically transmissive, astage of metamaterials positioned in proximity to or in contact with thesubstrate, a reflector positioned opposite the substrate and configuredto reflect an optical signal that passes through the stage ofmetamaterials to pass through the stage of metamaterials again and wherethe stage of metamaterials is configured to demultiplex a first opticalsignal having a first wavelength and a second wavelength into a secondoptical signal having the first wavelength and a third optical signalhaving the second wavelength based on shifting a phase profile of thefirst optical signal by the stage of metamaterials before and after thefirst optical signal reflects from the reflector, the second opticalsignal having a first portion of information conveyed by the firstoptical signal and the third optical signal having a second portion ofinformation conveyed by the first optical signal.

A method may include growing a substrate that is optically transmissive,depositing a layer of metamaterial on the substrate, depositing a resistlayer on the layer of metamaterial, etching a portion of the resistlayer to form a set of hardmasks, and etching the set of hardmasks andexposed portions of the layer of metamaterial to form a set ofmetamaterial structures based on etching the portion of the resistlayer, where the set of metamaterial structures are configured to shiftphase profiles of a first optical signal having a first wavelength and asecond optical signal having a second wavelength to multiplex the firstoptical signal and the second optical signal into a third optical signalhaving the first wavelength and the second wavelength.

An apparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to cause the apparatusto grow a substrate that is optically transmissive, deposit a layer ofmetamaterial on the substrate, deposit a resist layer on the layer ofmetamaterial, etch a portion of the resist layer to form a set ofhardmasks, and etch the set of hardmasks and exposed portions of thelayer of metamaterial to form a set of metamaterial structures based onetching the portion of the resist layer, where the set of metamaterialstructures are configured to shift phase profiles of a first opticalsignal having a first wavelength and a second optical signal having asecond wavelength to multiplex the first optical signal and the secondoptical signal into a third optical signal having the first wavelengthand the second wavelength.

Another apparatus may include means for growing a substrate that isoptically transmissive, means for depositing a layer of metamaterial onthe substrate, means for depositing a resist layer on the layer ofmetamaterial, means for etching a portion of the resist layer to form aset of hardmasks, and means for etching the set of hardmasks and exposedportions of the layer of metamaterial to form a set of metamaterialstructures based on etching the portion of the resist layer, where theset of metamaterial structures are configured to shift phase profiles ofa first optical signal having a first wavelength and a second opticalsignal having a second wavelength to multiplex the first optical signaland the second optical signal into a third optical signal having thefirst wavelength and the second wavelength.

A non-transitory computer-readable medium storing code is described. Thecode may include instructions executable by a processor to grow asubstrate that is optically transmissive, deposit a layer ofmetamaterial on the substrate, deposit a resist layer on the layer ofmetamaterial, etch a portion of the resist layer to form a set ofhardmasks, and etch the set of hardmasks and exposed portions of thelayer of metamaterial to form a set of metamaterial structures based onetching the portion of the resist layer, where the set of metamaterialstructures are configured to shift phase profiles of a first opticalsignal having a first wavelength and a second optical signal having asecond wavelength to multiplex the first optical signal and the secondoptical signal into a third optical signal having the first wavelengthand the second wavelength.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for depositing a reflectivematerial to form a reflector at one end of the set of metamaterialstructures based on etching the set of hardmasks and the exposedportions of the layer of metamaterial.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for depositing cladding onthe set of metamaterial structures and on exposed portions of thesubstrate based on etching the set of hardmasks and the exposed portionsof the layer of metamaterial, where depositing the reflective materialmay be based on depositing the cladding.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the reflective material maybe deposited on the cladding that may be positioned between the set ofmetamaterial structures and the reflective material.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the reflective material maybe deposited on the cladding that may be positioned between the set ofmetamaterial structures and the reflective material.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for depositing cladding onthe set of metamaterial structures and on exposed portions of thesubstrate based on etching the layer of metamaterial and the resistlayer, where depositing the reflective material may be based ondepositing the cladding.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, each metamaterial structureof the set of metamaterial structures may have one or more parametersthat includes a height of the metamaterial structure, a cross-sectionalprofile of the metamaterial structure, a diameter of the metamaterialstructure, a dielectric property of the metamaterial structure, or acombination thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, at least some of the one ormore parameters of each metamaterial structure may be based on a secondcross-sectional profile of an associated hardmask.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, at least some of the one ormore parameters of each metamaterial structure may be based on a secondcross-sectional profile of an associated cavity in the resist layer.

A method may include depositing a substrate that is opticallytransmissive, depositing a resist layer on the substrate, etching aportion of the resist layer to form a set of cavities in the resistlayer, depositing a layer of metamaterial on the resist layer that formsthe set of cavities, the layer of metamaterial filling at least some ofthe set of cavities formed in the resist layer, and etching the layer ofmetamaterial and the resist layer to form a set of metamaterialstructures based on depositing the layer of metamaterial on the resistlayer, where the set of metamaterial structures are configured to shiftphase profiles of a first optical signal having a first wavelength and asecond optical signal having a second wavelength to multiplex the firstoptical signal and the second optical signal into a third optical signalhaving the first wavelength and the second wavelength.

An apparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to cause the apparatusto deposit a substrate that is optically transmissive, deposit a resistlayer on the substrate, etch a portion of the resist layer to form a setof cavities in the resist layer, deposit a layer of metamaterial on theresist layer that forms the set of cavities, the layer of metamaterialfilling at least some of the set of cavities formed in the resist layer,and etch the layer of metamaterial and the resist layer to form a set ofmetamaterial structures based on depositing the layer of metamaterial onthe resist layer, where the set of metamaterial structures areconfigured to shift phase profiles of a first optical signal having afirst wavelength and a second optical signal having a second wavelengthto multiplex the first optical signal and the second optical signal intoa third optical signal having the first wavelength and the secondwavelength.

Another apparatus may include means for depositing a substrate that isoptically transmissive, means for depositing a resist layer on thesubstrate, means for etching a portion of the resist layer to form a setof cavities in the resist layer, means for depositing a layer ofmetamaterial on the resist layer that forms the set of cavities, thelayer of metamaterial filling at least some of the set of cavitiesformed in the resist layer, and means for etching the layer ofmetamaterial and the resist layer to form a set of metamaterialstructures based on depositing the layer of metamaterial on the resistlayer, where the set of metamaterial structures are configured to shiftphase profiles of a first optical signal having a first wavelength and asecond optical signal having a second wavelength to multiplex the firstoptical signal and the second optical signal into a third optical signalhaving the first wavelength and the second wavelength.

A non-transitory computer-readable medium storing code is described. Thecode may include instructions executable by a processor to deposit asubstrate that is optically transmissive, deposit a resist layer on thesubstrate, etch a portion of the resist layer to form a set of cavitiesin the resist layer, deposit a layer of metamaterial on the resist layerthat forms the set of cavities, the layer of metamaterial filling atleast some of the set of cavities formed in the resist layer, and etchthe layer of metamaterial and the resist layer to form a set ofmetamaterial structures based on depositing the layer of metamaterial onthe resist layer, where the set of metamaterial structures areconfigured to shift phase profiles of a first optical signal having afirst wavelength and a second optical signal having a second wavelengthto multiplex the first optical signal and the second optical signal intoa third optical signal having the first wavelength and the secondwavelength.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for depositing a reflectivematerial to form a reflector at one end of the set of metamaterialstructures based on etching the layer of metamaterial and the resistlayer.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, each metamaterial structureof the set of metamaterial structures may have one or more parameters ofthe metamaterial structure includes a height of the metamaterialstructure, a cross-sectional profile of the metamaterial structure, adiameter of the metamaterial structure, a dielectric property of themetamaterial structure, or a combination thereof.

An apparatus may include a first substrate that is opticallytransmissive, a first stage of metamaterials positioned in proximity toor in contact with the first substrate, a second stage of metamaterialspositioned in proximity to or in contact with the first substrate, thefirst stage of metamaterials and the second stage of metamaterialsconfigured multiplex a first optical signal having a first wavelengthand a second optical signal having a second wavelength into a thirdoptical signal having the first wavelength and the second wavelengthbased on shifting a first phase profile of the first optical signal anda second phase profile of the second optical signal by the first stageof metamaterials and the second stage of metamaterials.

In some examples, the first stage of metamaterials may be configured toshift the first phase profile of the first optical signal and the secondphase profile of the second optical signal and output a first shiftedoptical signal and a second shifted optical signal, and the second stageof metamaterials may be configured to shift a third phase profile of thefirst shifted optical signal and a fourth phase profile of the secondshifted optical signal and output the third optical signal and thefourth optical signal.

Some examples of the apparatus may include a second substrate that maybe optically transmissive positioned in proximity to or in contact withthe second stage of metamaterials, where the first substrate, the firststage of metamaterials, the second substrate, and the second stage ofmetamaterials form a stacked structure.

Some examples of the apparatus may include a spacer positioned inproximity to or in contact with the first substrate and the secondsubstrate and creating a space between a first surface of the firstsubstrate and a second surface of the second substrate, where the secondstage of metamaterials may be positioned in the space created by thespacer.

Some examples of the apparatus may include a liquid optically clearadhesive positioned in the space created by the spacer, where the secondstage of metamaterials may be positioned in proximity to or in contactwith the second surface of the second substrate and the liquid opticallyclear adhesive may be positioned between the second stage ofmetamaterials and the first surface of the first substrate.

Some examples of the apparatus may include a first reflector and asecond reflector configured to reflect the first optical signal and thesecond optical signal, the first substrate positioned between the firstreflector and the second reflector.

Some examples of the apparatus may include cladding positioned betweenthe first stage of metamaterials and the first reflector, the claddinghaving a thickness configured to mitigate losses of optical signalsinteracting with the first stage of metamaterials or to protect thefirst stage of metamaterials or a combination thereof.

In some examples, the first stage of metamaterials and the second stageof metamaterials may be positioned in proximity to or in contact withthe first reflector; or the first stage of metamaterials may bepositioned in proximity to or in contact with the first reflector andthe second stage of metamaterials may be positioned in proximity to orin contact with the second reflector.

In some examples, the first reflector forms a first aperture forreceiving the first optical signal and the second optical signal, andthe second reflector forms a second aperture for outputting the thirdoptical signal; or the first reflector forms the first aperture forreceiving the first optical signal and the second optical signal and thesecond aperture for outputting the third optical signal.

In some examples, the first substrate, the first reflector, the secondreflector, the first stage of metamaterials, and the second stage ofmetamaterials form a Fabry-Perot cavity configured to generate one ormore resonant reflections of the first optical signal and the secondoptical signal.

In some examples, the first stage of metamaterials may includeoperations, features, means, or instructions for a set of metamaterialstructures arranged in a pattern to shift a phase profile of an opticalsignal based on one or more parameters of each metamaterial structure ofthe set of metamaterial structures.

In some examples, the one or more parameters of the metamaterialstructure includes a height of the metamaterial structure, across-sectional profile of the metamaterial structure, a diameter of themetamaterial structure, a dielectric property of the metamaterialstructure, or a combination thereof.

In some examples, a total phase shifting caused by the first stage ofmetamaterials may be based on a phase shifting profile of eachmetamaterial structure and the pattern of the set of metamaterialstructures.

An apparatus may include a substrate that is optically transmissive, astage of metamaterials positioned in proximity to or in contact with thesubstrate and configured to demultiplex a first optical signal having afirst wavelength and a second wavelength into a second optical signalhaving the first wavelength and a third optical signal having the secondwavelength based on shifting a phase profile of the first optical signalby the stage of metamaterials before and after the first optical signalreflects from the reflector, the second optical signal having a firstportion of information conveyed by the first optical signal and thethird optical signal having a second portion of information conveyed bythe first optical signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an example of a schematic diagram of an opticalsystem that supports a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein.

FIG. 1B illustrates examples of diagrams of an uncoupled multicoreoptical communication link that support a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communicationsin accordance with examples as disclosed herein.

FIG. 1C illustrates examples of diagrams of a coupled multicore opticalcommunication link that support a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communicationsin accordance with examples as disclosed herein.

FIG. 2A illustrates an example of an optical device that may form atleast a portion of a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein.

FIG. 2B illustrates an example of an optical device that may form atleast a portion of a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein.

FIG. 2C illustrates an example of a phase profile of an optical devicethat supports a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein.

FIG. 3 illustrates an example of an optical device that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein.

FIGS. 4A-4E illustrate examples of optical devices that support awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein.

FIGS. 5A-5F illustrate an example of a method for manufacturing anoptical device that supports a wavelength multiplexer or demultiplexerthat uses metamaterials for optical fiber communications in accordancewith examples as disclosed herein.

FIGS. 6A-6F illustrate an example of a method for manufacturing anoptical device that supports a wavelength multiplexer or demultiplexerthat uses metamaterials for optical fiber communications in accordancewith examples as disclosed herein.

FIGS. 7 and 8 show flowcharts illustrating a method or methods thatsupports a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein.

DETAILED DESCRIPTION

Optical communications systems are widely deployed to provide varioustypes of communication content such as voice content, video content,packet data, messaging, broadcast content, and so on. Opticalcommunication systems rely on various types of multiplexing of opticalsignals onto a common transmission optical fiber to increase the amountof information that can be transmitted over the transmission opticalfiber. Some types of multiplexing may include wavelength divisionmultiplexing (WDM), polarization division multiplexing (PDM), frequencydivision multiplexing (FDM), time division multiplexing (TDM), spacedivision multiplexing (SDM), and mode division multiplexing (MDM).

WDM techniques can be used in both short-distance optical communicationsystems (e.g., for connections within data centers) and long-hauloptical communication systems (e.g., for inter-data center connections,metropolitan environments, submarine environments such as atranscontinental optical communication link). By using multiple opticalsignals at different wavelengths, the communication capacity of anoptical communication link can be effectively increased. In such opticalsystems, a wavelength multiplexer and wavelength demultiplexer may beused to perform WDM techniques. For example, a multiplexer may combineoptical signals having different wavelengths from different input fibersinto one output fiber, and a demultiplexer may separate an opticalsignal that has multiple different wavelengths from one or more inputfiber into different output fibers.

Systems, devices, and techniques for performing wavelength divisionmultiplexing or demultiplexing using one or more metamaterials inoptical communications systems are described. An optical device may beconfigured to shift one or more phase profiles of an optical signalusing one or more stages of metamaterials to multiplex or demultiplexrespective wavelengths of optical signals. The optical device may be anexample of a stacked design with two or more stages of metamaterialsstacked on top of one another. The optical device may be an example of afolded design that reflects optical signals between different stages ofmetamaterials.

Features of the disclosure are initially described in the context of anoptical system as described with reference to FIG. 1A. Features of thedisclosure are further described in the context of optical devices, aphase profile, and flowcharts, as described with reference to FIGS. 2A-8.

FIG. 1A illustrates an example of a schematic diagram of an opticalsystem 100 that supports a wavelength multiplexer or demultiplexer thatuses metamaterials for optical fiber communications in accordance withexamples as disclosed herein. The optical system 100 may include anoptical communications link 105, a transmitter system 110, and areceiver system 115.

The optical system 100 may utilize techniques of WDM to increase anamount of information communicated over a single optical communicationslink 105. WDM techniques may include multiplexing a quantity of opticalcarrier signals having different wavelengths onto fewer optical fibersor onto a single optical fiber. Such techniques may enable bidirectionalcommunications over a single optical fiber or multiplication of capacityover a single optical fiber in some examples. In effect, WDM may combinetwo or more optical signals operating in different optical frequencybands into a single optical signal communicated over an optical fiber.WDM techniques may also include demultiplexing techniques thatdemultiplex an optical signal, such as a single optical signal, withdifferent information in different optical frequency bands into moreoptical signals, such as two or more optical signals. WDM techniques mayincrease a communication capacity of an optical communications link 105.

The optical communications link 105 may be an example of an opticalfiber for communicating one or more optical signals. An optical fibermay convey light from one end to another end by guiding the lightthrough principles of internal reflection. One or more optical signalsconveyed by the optical communications link 105 may be modulated withinformation to support communications between the transmitter system 110and the receiver system 115. The optical communications link 105 mayinclude one or more multimode fibers (MMFs), one or more few-mode fibers(FMFs), one or more single-mode fiber (SMFs), one or more multi-corefibers (MCFs), or any combination thereof.

The transmitter system 110 may be configured to transmit an opticalsignal through the optical communications link 105. The transmittersystem 110 may include a multiplexer 120 and one or more transmitters125 that may be coupled using one or more optical communication links130. The optical communications link 130 may include SMFs, FMFs, MMFs,MCFs, or any combination thereof. The transmitters 125 may be configuredto transmit an optical signal that includes optical energy operating atan optical wavelength (e.g., optical frequency band) and modulated withinformation. In some cases, each transmitter 125 may be configured totransmit an optical signal that operates at a unique optical wavelength.For example, a first transmitter 125-a may be configured to transmit afirst optical signal at a first wavelength (e.g., λ₁) and a secondtransmitter 125-b may be configured to transmit a second optical signalat second wavelength (e.g., λ₂) different than the first wavelength. Thetransmitter system 110 may be an example of a system implemented at acentral office (CO), a headend, a switching center, or the like. Inother examples, the transmitter system 110 may be implemented at aconsumer premises equipment (CPE) or other device.

The multiplexer 120 may be configured to multiplex several opticalsignals together into a single optical signal. The multiplexer 120 mayreceive one or more optical signals from the transmitters 125 (e.g.,over the one or more optical communication links 130) and may output oneor more optical signals over the optical communications link 105. Themultiplexer 120 may be configured to implement WDM techniques to combinedifferent wavelengths from different optical signals into fewer opticalsignals, such as a single optical signal that includes the differentwavelengths.

The receiver system 115 may be configured to receive an optical signalconveyed by the optical communications link 105. The receiver system 115may include a demultiplexer 135 and one or more receivers 140, where theone or more receivers 140 may be coupled with the demultiplexer 135using one or more optical communication links 145. The opticalcommunications link 145 may include SMFs, FMFs, MMFs, MCFs, or anycombination thereof. The demultiplexer 135 may be configured to receiveone or more optical signals, such as a single optical signal, and splitthe optical signal(s) into several optical signals. In some examples,the demultiplexer 135 may receive an optical signal conveyed by theoptical communications link 105 and may output one or more opticalsignals to the receivers 140 (e.g., over the one or more opticalcommunication links 145). The demultiplexer 135 may be configured toimplement WDM techniques to split different wavelengths from a singleoptical signal into different optical signals that include the differentwavelengths.

The receivers 140 may be configured to receive an optical signal thatincludes optical energy operating at an optical wavelength (e.g.,optical frequency band) and modulated with information. In some cases,each receiver 140 may be configured to receive an optical signal thatoperates at a unique optical wavelength. For example, a first receiver140-a may be configured to receive a first optical signal at a firstwavelength (e.g., Xi) and a second receiver 140-b may be configured toreceive a second optical signal at second wavelength (e.g., λ₂)different than the first wavelength. In some cases, the receiver system115 may be an example of a system implemented at a CO, a headend, aswitching center, or the like. In other examples, the receiver system115 may be implemented at a CPE or similar device.

WDM techniques may be used in both short-distance optical communicationsystems (e.g., for connections within data centers) and long-hauloptical communication systems (e.g., for inter-data center connections,metropolitan environments, submarine environments such astranscontinental optical communication link). By using multiple opticalsignals at different wavelengths, the communication capacity of anoptical communications link 105 can be effectively increased. In suchWDM systems, a wavelength multiplexer (e.g., mux) or wavelengthdemultiplexer (e.g., demux) or both may be used to perform WDMtechniques. For example, the multiplexer 120 may combine optical signalshaving different wavelengths from different input fibers into one outputfiber, and a demultiplexer 135 may separate an optical signal that hasmultiple different wavelengths from one input fiber into differentoutput fibers. The fibers used in the optical system 100 may be examplesof an SMF, an FMF, an MMF, or an MCF, or any combination thereof. Inother examples, the multiplexer or demultiplexer may be used with MCFsto convert between different modes of different optical signal indifferent cores of an MCF.

Some optical systems may use one or more of several techniques toperform WDM techniques. Examples of devices that may implement WDMtechniques may include a thin film filter (TFF), an arrayed waveguidegrating (AWG), or a fused fiber optic coupler, among others.

TFF technology may use concatenated interference filters, each of whichmay be fabricated with a different set of dielectric coatings designedto pass a single wavelength and reflect all other wavelengths. By usinga series of parts with different thin film coatings, a TFF device may beused to separate or combine different wavelengths. TFFs may work wellfor low channel counts, but have limitations at higher channel counts,for example, due to size and accumulated insertion losses. In somecases, a few parts each having different thin film coating designs maybe used within a TFF mux or TFF demux device, hence the device may use amicro-optics level assembly. In some cases, TFF technology may not besuitable for narrow-band dense WDM applications. For instance, such TFFdevices may require several hundred layers of coatings to createnarrow-band filters that separate and isolate individual wavelengths.The yield of such filter may be limited due to errors induced by localfilm thickness variation and density alternation.

AWG technology may utilize interference effects to separate or combinewavelengths. In some AWG devices, incoming light may propagate through afree propagation region and enter a bundle of optical fibers or channelwaveguides, which have different lengths and thus apply a differentphase shift to the light in each fiber or waveguide. The light thentraverses another free propagation region and interferes at the entriesof the output, such that each output channel receives light of a certainwavelength. AWG technology may be suitable and cost-effective forhigh-channel-count applications, and may offer flexibility in selectingchannel numbers and spacing. In some cases, the whole AWG device can beintegrated on the same substrate. The performance of some AWG devices,however, may be sensitive to temperature. For example, if thetemperature of an AWG device fluctuates, the channel wavelength willchange according to the thermal coefficient of the material used.Therefore, temperature control or monitoring techniques (which resultsin extra power consumption) or athermal techniques (which may beachieved by compensation using different materials) are used to maintainperformance.

A fused coupler (also known as Fused Biconical Taper (FBT) technology)may include two, parallel optical fibers that have been twisted,stretched, and fused together. The cores may be so close to each otherthat an evanescent wave may “leak” from one fiber core into the otherfiber core, resulting in an exchange of energy. The amount of energyexchanged may be dependent upon the coupling strength (e.g., based onthe distance between the two cores) and coupling length (e.g.,interaction length). The energy exchange rate may also vary withwavelength. By adjusting the coupling strength and length, light fromdifferent wavelengths may be combined from different ports into anoutput port (WDM mux) or separated from one port into different outputports (WDM demux). However, since this technique uses coupling betweenfiber cores, the number of wavelength channels is typically limited totwo (2).

Optical system 100 may support systems, devices, and techniques forperforming wavelength division multiplexing or demultiplexing using oneor more metamaterials. In some examples, metamaterials may be or mayinclude metasurfaces. A device having metamaterials may use one or morephase masks (e.g., high-resolution phase masks) enabled by opticalmetamaterials to multiplex or demultiplex wavelengths of opticalsignals. The device may be an example of a stacked design with two ormore stages of metamaterials on top of one another. The device may be anexample of a folded design that reflects optical signals betweendifferent stages of metamaterials. The phase profiles of the stages ofmetamaterials in the device may be designed using adjoint optimizationtechniques, wavefront matching techniques, or any combination thereof,as described further herein.

Wavelength multiplexing and demultiplexing are useful functionalities inoptical communication systems. The wavelength multiplexing anddemultiplexing functionalities may be examples of functionalities wherelight propagating in an optical fiber containing multiple wavelengthsmay be demultiplexed into separate signals, each signal beingsubsequently included in individual output fibers (or vice-versa). Suchfunctionalities may be useful in a wide range of communicationapplications, such as long-distance communications networks employingWDM, access networks where multiple wavelengths are used, for example,in downstream (e.g., from a CO to a CPE, such as in afiber-to-the-premises (FTTP) architecture or other networkarchitectures) and upstream transmission (e.g., from a CPE to a CO inthe FTTP network architecture), as well as in data center applications.Each application may include different performance requirements leadingto different specification parameters for wavelength multiplexing anddemultiplexing functionalities, such as a number of wavelengths beingmultiplexed or demultiplexed, optical performance specifications (e.g.,insertion loss, crosstalk, channel bandwidth, channel spacing, others,or any combination thereof), environmental conditions, costrequirements, or density requirements. In particular, densityrequirements related to including more optical signals in smallervolumes are becoming more and more important in some data center andsome access applications.

A TFF device may be used to perform WDM techniques. In some cases, a TFFdevice, involving multiple micro-optics elements may have a relativelylarge size and may be difficult to integrate into systems withhigh-density requirements, such as in a data center. In some examples,emerging applications, such as fiber to the server architectures, mayuse a wavelength multiplexer or wavelength demultiplexer for hundreds ofoptical fibers, and devices with small form-factors may accordinglybecome useful in such applications. Multiplexers and demultiplexers thatuse metamaterials to perform WDM techniques may exhibit highly compactform-factors. For example, a 4-wavelength micro-opticsmultiplexer/demultiplexer may be 50 mm×25 mm×10 mm in size, whereas ametamaterial multiplexer/demultiplexer with relatively similar opticalperformance may be 1 mm×1 mm×0.5 mm in size. Such size differences mayenable integration of the metamaterial device in an optical connector.

In addition to a reduced form-factor, a metamaterial-basedmultiplexer/demultiplexer may provide other advantages. In someexamples, the metamaterial-based wavelength multiplexer/demultiplexerdevice may be designed to support multiple wavelength channels, may beeither coarse WDM (CWDM) or dense WDM (DWDM), and may be used for eitherSMF, or FMF, MMF, or an MCF, or hybrid fiber systems. Themetamaterial-based multiplexer/demultiplexer may be implemented throughintegrated optics on a single substrate, eliminating other micro-opticscomponents, such as multiple thin-film blocks, multiple collimators andmirrors, as well as significantly simplifying the fabrication andassembly process. In some examples, using wavefront matching techniques,adjoint analysis techniques (e.g., adjoint analysis optimization), orany combination thereof to design precise and high-resolution phase mapsof the metamaterials may enable more complex filter designs that are notfeasible with other technologies (e.g., such as thin-film stacks). Insome examples, metamaterials can be designed as polarizationinsensitive, so that a metamaterial-based multiplexer/demultiplexer willnot interfere with polarization multiplexing. It is noted that the termsmetamaterials and metasurfaces described herein may refer to materialsthat exhibit properties based on the structure (e.g., geometry,arrangement, size, shape, orientation, or the like) of the materialitself, which may be configured for various purposes, applications, ortechnologies.

FIG. 1B illustrates examples of diagrams 160 of an uncoupled multicoreoptical communication link 165 that support a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communicationsin accordance with examples as disclosed herein. The uncoupled multicoreoptical communication link 165 may be an example of the opticalcommunication links 105, 130, and 145 as described with reference toFIG. 1A.

An MCF may be an example of an optical fiber that contains multiplecores in one common cladding. An MCF may include a plurality of SMFs, aplurality of FMFs, a plurality of MMFs, or any combination thereof. Forexample, the uncoupled multicore optical communication link 165 mayinclude a first core 170-a, a second core 170-b, a third core 170-c, anda fourth core 170-d and a cladding 175 positioned in proximity to (e.g.,near, proximate, without having one or more materials between, havingone or more materials between) or in contact with each of the cores 170.The cores 170 of the uncoupled multicore optical communication link 165may be examples of SMFs, FMFs, MMFs or any combination thereof. Forcases, an MCF may include fibers have a single type (e.g., all SMFs) ormay include fibers of different types (e.g., one SMF and three MMFs).With MCFs, the design of the cores, the number of cores, core layout,outer cladding thickness (e.g., a minimum distance between the center ofthe outer cores and the cladding-coating interface), a claddingdiameter, or any combination thereof can be designed to achieve opticaland mechanical performance for the MCF. Desirable fiber design maydiffer depending on the application. An MCF may include any quantity ofcores (e.g., two, three, four, five, six, seven, eight, nine, ten,eleven, twelve, etc.).

An MCF may be an example of a coupled MCF or an uncoupled MCF. Some MCFsmay experience issues related to inter-core crosstalk or otherinterference. An uncoupled MCF may be an MCF where each individual coreis assumed to be an independent optical path. A coupled MCF may be anMCF where one core is assumed to be at least partially dependent onanother core. In some examples, the distance between at least some coresin an uncoupled MCF may be greater than the distance between at leastsome cores in the coupled MCF.

The uncoupled multicore optical communication link 165 may be an exampleof an uncoupled MCF. In some cases, parameters of different cores 170may be the same. In other examples, at least one core 170 of theplurality of cores 170 may have different parameters as the other cores.Examples of parameters of the cores 170 may include a diameter of thecore, a dielectric property of the core, a relative difference betweenthe dielectric property of the core 170 and a dielectric property of thecladding 175, a distance from a center of a core to a center of theuncoupled multicore optical communication link 165, a mode-rating of thecore, a refractive index profile (e.g., Δn), or a combination thereof.In some examples, a diameter of each core 170 may be about 8.2micrometers, a refractive index profile of the cores 170 may be about0.35% (e.g., Δn=0.35%), and a core center to center distance may beabout 45 micrometers.

The first diagram 160-a may illustrate an intensity distribution of anoptical signal in the first core 170-a, where the other cores (e.g.,cores 170-b, 170-c, and 170-d) are not communicating optical signals.The second diagram 160-b may illustrate an intensity distribution of anoptical signal in the second core 170-b, where the other cores (e.g.,cores 170-a, 170-c, and 170-d) are not communicating optical signals.The third diagram 160-c may illustrate an intensity distribution of anoptical signal in the third core 170-c, where the other cores (e.g.,cores 170-a, 170-b, and 170-d) are not communicating optical signals.The fourth diagram 160-d may illustrate an intensity distribution of anoptical signal in the fourth core 170-d, where the other cores (e.g.,cores 170-a, 170-b, and 170-c) are not communicating optical signals.

FIG. 1C illustrates examples of diagrams 180 of a coupled multicoreoptical communication link 185 that support a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communicationsin accordance with examples as disclosed herein. The coupled multicoreoptical communication link 185 may be an example of the opticalcommunication links 105, 130, and 145 as described with reference toFIG. 1A.

The coupled multicore optical communication link 185 may include a firstcore 190-a, a second core 190-b, a third core 190-c, and a fourth core190-d and a cladding 195 positioned in proximity to or in contact witheach of the cores 190. The cores 190 of the coupled multicore opticalcommunication link 185 may be examples of SMFs, FMFs, MMFs or anycombination thereof. For cases, an MCF may include fibers have a singletype (e.g., all SMFs) or may include fibers of different types (e.g.,one SMF and three MMFs).

The coupled multicore optical communication link 185 may be an exampleof a coupled MCF. In some cases, parameters of different cores 190 maybe the same. In other examples, at least one core 190 of the pluralityof cores 190 may have different parameters as the other cores. Examplesof parameters of the cores 190 may include a diameter of the core, adielectric property of the core, a relative difference between thedielectric property of the core 190 and a dielectric property of thecladding 195, a distance from a center of a core to a center of thecoupled multicore optical communication link 185, a mode-rating of thecore, a refractive index profile (e.g., Δn), or a combination thereof.In some examples, a diameter of each core 190 may be about 8.2micrometers, a refractive index profile of the cores 170 may be about0.35% (e.g., Δn=0.35%), and a core center to center distance may beabout 20 micrometers.

The diagrams 180 (e.g., a first diagram 180-a, a second diagram 180-b, athird diagram 180-c, and a fourth diagram 180-d) may illustratedifferent intensity distributions of optical signal in different cores190. In the first diagram 180-a, the distributions in each of the cores190 may be about the same. In the second diagram 180-b, the second core190-b may have an intense distribution (e.g., around 0.9) at the center,the third core 190-b may have an intense distribution (e.g., around−0.9) at the center, the fourth core 190-d may have a mediumdistribution (e.g., around −0.5) at the center, and the first core 190-amay have a medium distribution (e.g., around 0.5) at the center. In thethird diagram 180-c, the fourth core 190-d may have an intensedistribution (e.g., around 0.9) at the center, the first core 190-a mayhave an intense distribution (e.g., around −0.9) at the center, thethird core 190-c may have a medium distribution (e.g., around −0.5) atthe center, and the second core 190-b may have a medium distribution(e.g., around 0.5) at the center. In the fourth diagram 180-d, the firstcore 190-a may have an intense distribution (e.g., around −0.9) at thecenter, the second core 190-b may have an intense distribution (e.g.,around 0.9) at the center, the third core 190-c may have an intensedistribution (e.g., around 0.9) at the center, and the fourth core 190-dmay have an intense distribution (e.g., around −0.9) at the center.

FIG. 2A illustrates an example of an optical device 201 that may form atleast a portion of a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein. The optical device 201 may be an exampleof a multiplexer/demultiplexer device that uses metamaterials asdescribed with reference to FIG. 1A. In some cases, the optical device201 may be an example of a wavelength multiplexer/demultiplexer device.

The optical device 201 may include a substrate 205 and a plurality ofmetamaterial structures 210. In some cases, the optical device 201 mayalso include cladding (not shown). In some cases, the cladding may beair or some other environmental gas that surrounds the metamaterials.Metamaterials (sometimes referred to as metasurfaces) may benanophotonic structures that may control the properties of light (e.g.,a phase of light or a direction of travel of light) that passes throughthe metamaterials with a relatively high spatial resolution (e.g.,sub-wavelength, on the order of hundreds nanometers depending on anoperation wavelength window). In some examples, at least some if noteach metamaterial structure 210 may have one or more parameters thataffect how the properties of light are changed as the light passesthrough the metamaterial structure 210. An array of metamaterialstructures 210 may be arranged in a pattern (thereby forming a stage ofmetamaterials) to produces a desired shift in the properties of anoptical signal as it interacts with the stage of metamaterials.

In some cases, metamaterials may refer to a class of materials to haveproperties that may not be found in naturally occurring materials. Anoptical metamaterial may be smaller than the wavelength of light, butmay be able to interact with light and affect the light. Examples of theinteractions with light by metamaterials may include negativerefraction, fast and slow light propagation in zero index, trappingstructures, flat lenses, thin lenses, perfect lenses, or any combinationthereof.

An individual metamaterial structure 210 may affect light passingthrough the metamaterial structure based on one or more properties ofthe metamaterial structure 210. Examples of the properties of themetamaterial structure 210 that may affect light may include a height ofthe metamaterial structure (e.g., a dimension of the metamaterialstructure 210 that extends away from the substrate 205), across-sectional profile of the metamaterial structure 210 (e.g., across-sectional shape of the metamaterial), a cross-sectional area ofthe metamaterial structure 210, a volume of the metamaterial structure210, a diameter of the metamaterial structure 210, a dielectric propertyof the metamaterial structure 210, a relative difference between thedielectric property of the metamaterial structure 210 and a dielectricproperty of the substrate 205, a relative difference between thedielectric property of the metamaterial structure 210 and a dielectricproperty of cladding, or any combination thereof. In some cases, ametamaterial structure 210 may be an example of a multi-levelmetamaterial structure, where a first metamaterial structure with afirst set of parameters is stacked on top of a second metamaterialstructure 210 with a second set of parameters. A multi-levelmetamaterial structure may include any quantity of metamaterialstructures. In some cases, different metamaterial structures in a stackmay have different dielectric properties or other properties.

The metamaterial structures 210 illustrated in FIG. 2A show examples ofmetamaterial structures having circular, rectangular, and hexagonalcross-sectional shapes, different cross-sectional areas, and differentheights. These illustrative metamaterial structures 210 are merelyexamples of some of the properties of metamaterial structures. Forexample, in some cases, metamaterial structures 210 may have anycross-sectional profile, such as a circle, triangle, square, rectangle,pentagon, hexagon, other geometric cross-sectional profile, other shapedcross-sectional profile, or any combination thereof. As illustrated inFIG. 2A, each metamaterial structures 210 may correspond to a unit cell212 of a set of unit cells for a stage of metamaterial structures.Additionally or alternatively, a unit cell 212 of a set of unit cellsfor a stage of metamaterial structures may include two or moremetamaterial structures 210. In some examples, the metamaterialstructures 210 may have one or more parameters that are the same and maybe one or more parameters that are different. For example, in some case,all the metamaterials structures 210 may have a same cross-sectionalarea shape (e.g., circular shape), but may have a differentcross-sectional area (e.g., different size, different diameter). Forexample, in some case, all the metamaterials structures 210 may have asame height (e.g., relative to the substrate), but may have a differentcross-sectional area (e.g., different size, different diameter). In someexamples, one or more parameters related to a set or a subset of themetamaterial structures 210 may be the same or may be different.

The substrate 205 may be an example of material that forms a supportingbase for optical elements (such as metamaterials), other components, orany combination thereof. In some cases, the metamaterial structures 210are coupled with the substrate 205. In some cases, the substrate 205 maybe optically transmissive such that optical signals may pass through thesubstrate 205.

Each individual metamaterial structure 210 may be relatively small. Toshift a phase profile of an optical signal, a plurality of metamaterialstructures 210 may be arranged in a pattern and be configured to shiftthe phase profile of the optical signal. Arrays or patterns ofmetamaterial structures 210 may be referred to as stages of metamaterialstructures. Each individual metamaterial structure 210 may be have itsown set of parameters to affect the light. The overall phase-shiftingprofile of the stage of metamaterials may be based on the parameters ofeach individual metamaterial structure 210 in the stage. In some cases,cladding may be positioned in proximity to or in contact with themetamaterial structures 210, the substrate 205, or any combinationthereof. The cladding may be configured to mitigate losses of opticalsignals interacting with the metamaterial structures 210 or to protectthe metamaterial structures 210 from damage, or any combination thereof.In some cases, metamaterial structures 210 may be examples of reflectivemetamaterial structures and may be configured to be either achromatic orhighly dispersive.

Each metamaterial structure 210 is illustrated as individualfree-standing structures. In some examples, at least some or all of themetamaterial structures 210 may be formed of a single larger area. Insuch examples, a unit cell may refer to an individual configurableportion of the larger area of metamaterial that may be altered toachieve a desired phase profile.

FIG. 2B illustrates an example of an optical device 202 that may form atleast a portion of a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein. The optical device 202 may be an exampleof a multiplexer/demultiplexer device that uses metamaterials asdescribed with reference to FIGS. 1A and 2A. In some cases, the opticaldevice 202 may be an example of a wavelength multiplexer/demultiplexerdevice.

The optical device 202 may include a substrate 205, a plurality ofmetamaterial structures 210, cladding 215 surrounding the metamaterialstructures 210, and a reflector 220. The optical device 202 may be anexample of a stage of metamaterials that use a reflective design. Insuch designs, light may pass through the metamaterial structures 210,reflect off of the reflector 220, and pass through the metamaterialstructures 210 again after being reflected. In such designs, the phaseprofile of a stage of metamaterials may be based on both the phase shiftcaused by the light first (e.g., initially) passing through themetamaterial structures 210 and on the phase shift caused by thereflected light passing through the metamaterial structures 210 again.The features of the substrate 205 and the metamaterial structures 210are described with reference to FIG. 2A and are incorporated herein byreference.

The cladding 215 may be a layer of material. In some cases, the cladding215 may have a lower refractive index than the metamaterial structures210. In some cases, the cladding 215 may be configured to mitigatelosses of optical signals interacting with the metamaterial structures210. In some cases, the cladding 215 may be configured to protect themetamaterial structures 210 from damage.

In some examples, cladding 215 may be positioned between a surface 225of a metamaterial structure 210 and the reflector 220. In such examples,a distance 230 may be formed between the surface 225 of the metamaterialstructure 210 and a surface 235 of the reflector 220. The distance 230may be configured to mitigate losses of optical signals passing throughthe metamaterial structures 210 and being reflected by the reflector220. In some cases, the distance 230 may be about 500 nanometers. Insome cases, the distance 230 may be between zero nanometers and a fewmicrometers (e.g., one, two, or three micrometers). The surface 225 ofthe metamaterial structure 210 may be positioned opposite a differentsurface of the metamaterial structure 210 that contacts the substrate205.

The reflector 220 may be formed from one or more reflective materials.Examples of reflective materials may include gold or another metal. Insome cases, the reflective material may be coated with another materialto help to reflect the light. The light fields in FIG. 2B areillustrated as perpendicular to the metamaterials structures 210,substrate 205, cladding 215, and/or the reflector 220. In some examples,the light fields may arrive and/or leave at an angle that is notperpendicular with the metamaterials structures 210, substrate 205,cladding 215, and/or the reflector 220.

Each metamaterial structure 210 is illustrated as individualfree-standing structures. In some examples, at least some or all of themetamaterial structures 210 may be formed of a single larger area. Insuch examples, a unit cell may refer to an individual configurableportion of the larger area of metamaterial that may be altered toachieve a desired phase profile.

FIG. 2C illustrates an example of a phase profile 203 of an opticaldevice that supports a wavelength multiplexer or demultiplexer that usesmetamaterials for optical fiber communications in accordance withexamples as disclosed herein. The shading of the phase profile 203 mayshow different phase shifts caused by different portions of an opticaldevice (e.g., optical device 201 or 202). The phase profile 203 may bean example of a phase profile designed through wavefront matchingtechniques or adjoint analysis (e.g., adjoint optimization), asdescribed herein.

A plurality of metamaterial structures may be arranged in a pattern andbe configured to shift the phase profile of the optical signal. Arraysor patterns of metamaterial structures may be referred to as stages ofmetamaterial structures. Each metamaterial structure of a stage ofmetamaterials elements may be configured to shift a phase of a portionof an optical signal. In some cases, an individual metamaterialstructure may be viewed as an individual pixel (or a unit cell) of alarger stage of metamaterials. In some cases, the dimensions of themetamaterial structures can be on the order of hundreds of nanometersdepending on the operation wavelength window (e.g., when for a workingwavelength of 1550 nm, the unit cell size may be 500 nm×500 nm). Theoverall phase shift performed by a stage of metamaterials may be basedon the combination of each individual phase shift performed by eachindividual metamaterial structure of the stage of metamaterialstructures. Stages of metamaterials may be designed with different phaseprofiles by altering the parameters of individual metamaterialstructures in the stages of metamaterials. In some examples, lighttransmits through the substrate as well as the metamaterial structures(e.g., metamaterial pillars), and the phase change in each unit cell isdetermined by the geometry of the structure (e.g., cross-sectionalprofile, cross-sectional area, height, etc.).

The phase profile 203 is an example of phase profile caused by one ormore stages of metamaterials. Stages of metamaterials may have differentphase profiles based on the parameters of the various metamaterialstructures that form the stage of metamaterials. In some cases, thewavelength-dependent behavior of the phase (or the dispersion) can betuned, such that the metamaterial device may be either achromatic orrelatively highly dispersive. In addition, metamaterial structures maybe designed to work in reflection mode, when light passes through thepillars and reflects back with the help of one or more reflectivematerials, such as metal.

Depending on an operation wavelength window, different materials may bechosen for the substrate and the metamaterial structures. For example,for O band (1260-1360 nm), C band (1530-1565 nm), or L band (1565-1625nm) windows, crystalline silicon, amorphous silicon, silicon nitride(Si₃N₄), and chalcogenide glasses can be used for the metamaterialstructures. For shorter wavelength window (e.g., 850-940 nm), othermaterials such as titanium oxide (TiO₂) and silicon nitride (Si₃N₄) canused for the metamaterial structures. Transparent materials such asglass or polymer (e.g., SU8) may be used for the substrate and cladding.

In some cases, different design techniques may be used to design a phaseprofile of a stage of metamaterials. Examples of the design techniquesmay include wavefront matching, adjoint analysis (e.g., adjointoptimization), or any combination thereof.

To differentiate multiple wavelengths, a relatively highly dispersivesystem may be used. In some cases, a device may use different techniques(or any combination thereof) for creating such dispersion. First, eachmetamaterial structure itself may have dispersion (i.e., the phase valueassociated with each metamaterial structures at different wavelength maybe different), which may be similar to material dispersion. Second, thepropagation of light within the substrate may have dispersion (i.e., thepropagation path and hence the propagation phase through the substrateat different wavelength may be different), which may be similar tograting dispersion. By selecting parameters of metamaterial structuresin a stage of metamaterials, an optical device may achieve sufficientdispersion to make a compact and efficient WDM device.

Wavelength multiplexing and demultiplexing in fibers can be realized byutilizing a series of phase plates (e.g., stages of metamaterials)together with free space propagation to modify the wavefront of thelight field. To achieve low-loss and loss-crosstalk wavelengthmultiplexing or wavelength demultiplexing, multiple stages ofmetamaterials may be used (whether in a stacked design or a foldeddesign). The phase profiles for the stages of metamaterials used forwavelength multiplexing or wavelength demultiplexing can be designed byvarious methods including a wavefront matching method, adjoint analysismethod (e.g., adjoint optimization method), or any combination thereof.In some cases, stages of metamaterials can be initialized withgrating/lens features.

In a wavefront matching method, the input fields propagating forward maybe compared with the target fields propagating backward to obtain thefield difference at each stage of metamaterials. The difference may becompensated for by the design of the stage of materials phase plate,resulting in an accurate match of the fields. Such steps may beperformed iteratively to arrive at a design. A stage of metamaterialsmay be designed with a phase profile that can yield low loss and lowcrosstalk performance of the device based on performing analysis usingthe wavefront matching method.

In an adjoint analysis (e.g., adjoint optimization), a figure of merit(FOM) of the design may be defined as the power throughput for eachindividual input and output pair. Given the FOM, the derivative of theFOM with respect to each design parameter can be calculated. In somecases, the derivative of the FOM may be calculated from the propagatedfields at each metamaterial structure. Given the derivatives, anefficient gradient based nonlinear enhancement routine (e.g., aConjugate Gradient (CG), Newton-CG, Sequential Least SQuares Programming(SLSQP), a Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, etc.) maybe used to search for the enhanced phase profile. Depending on theapplication, additional FOMs can be added efficiently (e.g., when it canbe written as an analytic expression of the design variables or thefield variables). For example, to reduce the complexity of the phasemask, a FOM term that corresponds to the mean difference of phase valuesbetween every pair of adjacent pixels (or cells) may be added to theanalysis. In other examples, instead of enhancing for the average lossfor all the channels, the worst case (maximal) loss among all channelscan be minimized or the loss according to a specific distribution, forexample the channel bandwidths, can be enhanced.

FIG. 3 illustrates an example of an optical device 300 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical device 300 may use optically-transmissivemetamaterial structures and optically-transmissive substrates stacked ontop of one another to perform wavelength multiplexing or wavelengthdemultiplexing techniques. The optical device 300 may be an example ofthe optical device 201 described with reference to FIG. 2A. The diagramillustrated in FIG. 3 may be a cross-sectional view of the opticaldevice 300.

The optical device 300 may include a plurality of substrates 305positioned in proximity to or in contact with a plurality of stages 310of metamaterials. Each stage 310 of metamaterials may include aplurality of metamaterial structures. The plurality of substrates 305and the plurality of stages 310 may be stacked on top of one another.The optical device 300 may also include one or more spacers 315 and oneor more optically clear adhesives (OCAs) 320 positioned between eachlayer of a substrate 305 and stage 310 of metamaterials. The opticaldevice 300 may include any quantity of layers of metamaterials toperform wavelength multiplexing or wavelength demultiplexing techniques.For example, the optical device may include a first stage 310-a, asecond stage 310-b, a third stage 310-c, or any quantity of stages310-N. In such examples, the optical device 300 may include anynumerical of substrates 305, spacers 315, and OCAs 320 to support thestages 310. In some examples, the quantity of substrates 305 may be thesame as the quantity of stages 310 of metamaterials. The quantity oflayers may be determined based on a desired phase profile of the opticaldevice 300.

The substrate 305 may be an optically-transmissive substrate that isconfigured to support the stage 310 of metamaterials. The substrate 305may have one or more parameters that define the structure, such as aheight (h). The substrate 305 may be an example of the substrate 205described with reference to FIGS. 2A and 2B. In some examples, eachsubstrate 305 in the optical device 300 may have the same parameters.Additionally or alternatively, one or more substrates 305 may have adifferent parameter than other substrates in the optical device 300(e.g., the height (h) of one or more substrates 305 may be different)based on a desired phase profile of the optical device 300.

The stages 310 of metamaterials may include one or moreoptically-transmissive metamaterial structures that are configured toshift a phase profile of an optical signal (e.g., light) that passesthrough the metamaterial structures. Each stage 310 of metamaterials maybe positioned in proximity to or in contact with at least one substrate305. The metamaterial structures of the stages 310 may be examples ofthe metamaterial structures 210 described with reference to FIGS. 2A and2B. The metamaterial structures of the stages 310 of metamaterials mayhave one or more parameters that define the metamaterial structures,such as a cross-sectional profile, a cross-sectional area, or a height,among other examples. In some examples, each stage 310 of metamaterialsmay be designed with a different phase profile and the combined phaseprofiles of each stage 310 may result in an overall phase profile of theoptical device 300. In some examples, one or more stages 310 ofmetamaterials may have a different parameter than other stages 310 ofmetamaterials in the optical device 300 based on a desired phase profileof the optical device 300. In some examples, each stage 310 ofmetamaterials in the optical device 300 may have the same parameters.

The spacer 315 may be positioned between two different substrates 305and may be configured to create a space 325 between different substrates305. The spacer 315 may be positioned in proximity to or in contact witha first substrate 305 and a second substrate 305 to create the space325. A stage 310 of metamaterials may be positioned in the space 325created by the spacer 315. The spacer 315 may have one or moreparameters that define the structure, such as a height. In someexamples, each spacer 315 in the optical device 300 may have the sameparameters. In some examples, one or more spacers 315 may have adifferent parameter than other spacers 315 in the optical device 300(e.g., the height of one or more spacers 315 may be different). Anyquantity of spacers 315 may be positioned between different substrates.

The OCA 320 may be positioned in the space 325 created by the spacer315. The OCA 320 may be an example of a liquid OCA, or a gel OCA, or anycombination thereof. The OCA 320 may be an optically-transmissivematerial. The OCA 320 may be configured to protect the stages 310 ofmetamaterials. The OCA 320 may be positioned such that a stage 310 ofmetamaterials is positioned in proximity to or in contact with a surfaceof the substrate 305 and also positioned in proximity to or in contactwith OCA 320. In such examples, the OCA 320 may be positioned betweenone or more surfaces of a stage 310 of metamaterials and a bottomsurface of substrate 305. For example, the OCA 320 may be positionedbetween one or more to surfaces of the metamaterial structures of thesecond stage 310-b of metamaterials and a bottom surface of thesubstrate 305. In some cases, the OCA 320 may be an example of anindex-matching substance, where a refractive index of the OCA 320 may besimilar to that of one or more surrounding materials.

The optical device 300 may be configured as a wavelength multiplexer. Insome cases, the optical device 300 may be configured as a wavelengthdemultiplexer. In such cases, the inputs and outputs of the opticaldevice 300 may be reversed. An input fiber 330 may be positioned a firstdistance (d₁) away from the first stage 310-a of metamaterials and maybe configured to transmit one or more optical signals through theoptical device 300. The input fiber 330 may be an example of an opticalcommunications link 105, optical communications link 130, or opticalcommunications link 145 described with reference to FIG. 1A. An outputfiber 335 may be positioned a second distance (d₂) away from the lastlayer (e.g., the last substrate 305) of the optical device 300 and maybe configured to receive one or more optical signals output from theoptical device 300. The output fiber 335 may be an example of an opticalcommunications link 105, optical communications link 130, or opticalcommunications link 145 described with reference to FIG. 1A. In somecases, the input fiber 330, the output fiber 335, or any combinationthereof, may be examples of fiber arrays with a plurality of opticalfibers. In some cases, the first distance (d₁) may be the same size asthe second distance (d₂). In some cases, the first distance (d₁) may bea size different than the size of the second distance (d₂). In somecases, the input fiber 330 may include one or more SMFs and the one ormore input signals may be single-mode input signals. In other examples,the input fiber 330 may include one or more FMFs or MMFs and at leastone input signal may be a multi-mode signal. Additionally oralternatively, the output fiber 335 may include one or more SMFs and theone or more output signals may be single-mode output signals. In otherexamples, the output fiber 335 may include one or more FMFs or MMFs andat least one output signal may be a multi-mode signal. In some cases,additional spacers, additional OCAs, or a combination thereof may bepositioned between the input fiber 330 and the first stage 310-a ofmetamaterials. In some cases, additional spacers, additional OCAs, or acombination thereof may be positioned between the output fiber 335 andthe last layer (e.g., the last substrate 305) of the optical device 300.Such additional spacers or additional OCAs may be configured to reduceback reflection, protect the metamaterials, or provide the spacingsbetween fibers and the optical device, or any combination thereof.

In examples where the optical device 300 is configured as a wavelengthmultiplexer, the input fiber 330 may be an example of a fiber array andmay transmit two or more optical signals having different wavelengthsinto the optical device 300. The two or more optical signals may passthrough the different stages 310 of metamaterials (and other components)of the optical device 300. At each stage 310, the phase profiles of thetwo or more optical signals may be shifted or altered. The opticaldevice 300, through the different stages 310, may combine the two ormore optical signals into a single optical signal having the differentwavelengths. The output fiber 335 may be an example of a single outputfiber and may be configured to receive the optical signal that has beenmultiplexed to include the multiple wavelengths.

In examples where the optical device 300 is configured as a wavelengthdemultiplexer, the input fiber 330 may be an example of a single fiberand may transmit one optical signal that has different wavelengths intothe optical device 300. The optical signal may pass through thedifferent stages 310 of metamaterials (and other components) of theoptical device 300. At each stage 310, the phase profile of the opticalsignal may be shifted or altered. The optical device 300, through thedifferent stages 310, may separate the optical signal into two or moredifferent optical signals having the different wavelengths. The outputfiber 335 may be an example of a fiber array and may be configured toreceive the two or more optical signals that have been demultiplexedfrom the original optical signal.

In some cases, the optical device 300 may be used for WDM application.The optical device 300 may coherently adjust multiplex/demultiplexwavelengths of light into the same optical signal or out of the sameoptical signal into different optical signals. The light in the firststage of metamaterials may propagate in many directions, and mayinterfere with each other while traveling to or on the second stage ofmetamaterials. The second stage of metamaterials may propagate light inmany directions, which light may interfere with each other whiletraveling to or on the third stage of metamaterials. The spacer 315 maybe configured to allow the light propagating between stages 310 ofmetamaterials to interfere with each other.

FIGS. 4A-4E illustrate examples of optical devices that support awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical devices illustrated in FIGS. 4A-4E may be examplesof folded designs for optical devices that use reflective surfaces tocommunicate light between different stages of metamaterials. The opticaldevices illustrated in FIGS. 4A-4E may be examples of the optical device202 described with reference to FIG. 2B. FIGS. 4A-4E illustrate avariety of different configurations for a folded design of an opticaldevice that operates as a wavelength multiplexer or a wavelengthdemultiplexer. The disclosure is not limited to the express opticaldevice configurations illustrated. Any feature of any optical deviceconfiguration illustrated in FIGS. 4A-4E may be combined with any otherfeature of any optical device configuration illustrated in FIGS. 4A-4E.Aspects of the optical devices are initially described with reference toFIG. 4A, but are omitted from the descriptions of optical devices inFIGS. 4B-4E. Similarly numbered or similarly embodied features in theoptical devices in FIGS. 4A-4E may be treated similarly. FIGS. 4A-4Eillustrate optical devices having four stages of metamaterials. Theoptical devices of FIGS. 4A-4E, however, can be configured any number ofstages of metamaterials (e.g., one stage, two stages, three stages, fourstages, five stages, six stages, seven stages, eight stages, ninestages, etc.). The diagrams illustrated in FIGS. 4A-4E may be across-sectional views of the optical devices.

FIG. 4A illustrates an example of an optical device 401 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical device 401 may use optically-transmissivemetamaterial structures, an optically-transmissive substrate, andreflectors in a folded design to perform wavelength multiplexing orwavelength demultiplexing techniques. The optical device 401 may be anexample of the optical device 202 described with reference to FIG. 2B.

The optical device 401 may include a substrate 405 positioned inproximity to or in contact with a plurality of stages 410 ofmetamaterials, a first reflector 415, and a second reflector 420. Eachstage 410 of metamaterials may include a plurality of metamaterialstructures. The substrate 405, the plurality of stages 410, the firstreflector 415, and the second reflector 420 may illustrate a foldeddesign where light bounces between the two reflectors 415 and 420 andinteracts with the stages 410 of metamaterials based on the lightfollowing the reflected paths. The optical device 401 may include anyquantity of stages 410 of metamaterials to perform wavelengthmultiplexing or wavelength demultiplexing techniques. For example, theoptical device may include a first stage 410-a, a second stage 410-b, athird stage 410-c, or any quantity of stages 410-N.

The substrate 405 may be an optically-transmissive substrate that isconfigured to support the stage 410 of metamaterials. The substrate 405may have one or more parameters that define the structure, such as aheight or a cross-sectional area. The substrate 405 may be an example ofthe substrate 205 described with reference to FIGS. 2A and 2B.

The stages 410 of metamaterials may include one or moreoptically-transmissive metamaterial structures that are configured toshift a phase profile of an optical signal (e.g., light) that passesthrough the metamaterial structures. Each stage 410 of metamaterials maybe positioned in proximity to or in contact with the substrate 405. Themetamaterial structures of the stages 410 may be examples of themetamaterial structures 210 described with reference to FIGS. 2A and 2B.The metamaterial structures of the stages 410 of metamaterials may haveone or more parameters that define the metamaterial structures, such asa cross-sectional profile, a cross-sectional area, or a height. In someexamples, each stage 410 of metamaterials may be designed with adifferent phase profile and the combined phase profiles of each stage410 may result in an overall phase profile of the optical device 401. Insome examples, one or more stages 410 of metamaterials may have adifferent parameter than other stages 410 of metamaterials in theoptical device 401 based on a desired phase profile of the opticaldevice 401. In some examples, each stage 410 of metamaterials in theoptical device 401 may have the same parameters.

A first reflector 415 may be connected with the substrate 405. The firstreflector 415 may be configured to reflect an optical signal in theoptical device 401 along an optical path and on to a subsequent stage410 of metamaterials, to the second reflector 420, or any combinationthereof. In some cases, the first reflector 415 may be formed of areflective material that has a relatively greater property of reflectinglight, such as gold. In some cases, the first reflector 415 may becoated with a reflective material that has a relatively greater propertyof reflecting light (such as gold).

The second reflector 420 may be positioned near or adjacent to thestages 410 of metamaterials. The second reflector 420 may be configuredto reflect an optical signal in the optical device 401 along an opticalpath and on to a subsequent stage 410 of metamaterials, to the firstreflector 415, or any combination thereof. In some cases, the secondreflector 420 may be formed of a reflective material that has arelatively greater property of reflecting light, such as gold. In somecases, the second reflector 420 may be coated with a reflective materialthat has a relatively greater property of reflecting light (such asgold).

In some examples, the optical device 401 may include cladding 425 thatmay be configured to protect the metamaterial structures of the stages410 from damage, mitigate losses of optical signals interacting with themetamaterial structures, or any combination thereof. In some cases, thecladding 425 may be positioned between a surface of a metamaterialstructure and the second reflector 420 that is adjacent to the stages410 of metamaterials. In such cases, a distance (e.g., a distance 230described with reference to FIG. 2B) may be formed between the surfaceof the metamaterial structure and a surface of the second reflector 420.The surface of the metamaterial structure near the second reflector 420may be positioned opposite a different surface of the metamaterialstructure that contacts the substrate 405.

The first reflector 415, the second reflector 420, and the stages 410 ofmetamaterials may be configured to direct the optical signal along thedesired optical path in the optical device 401. In some cases, one ormore locations of the first reflector 415 and the second reflector 420may be configured to redirect light in a different direction. Forexample, an optical signal may impact a reflector at an approximatelyorthogonal angle to the plane of the reflector and the reflector may beconfigured to direct the optical signal in a different direction. Insome examples, a stage 410 of metamaterials may be configured to alter adirection of the optical signal. In some cases, the first reflector 415,the second reflector 420, or at least one stage 410 of metamaterials, orany combination thereof, may be configured to change a direction oftravel of the optical signal.

The optical device 401 may include an input aperture 430 for receivingan input optical signal into the optical device 401 or an outputaperture 435 for outputting an output optical signal from the opticaldevice 401 or both. In an illustrative example the optical device 401,the input aperture 430 and the output aperture 435 are formed by thefirst reflector 415. One or more sidewalls 440 of the first reflector415 may form the input aperture 430. Likewise, one or more sidewalls 445of the first reflector 415 may form the output aperture 435. In someexamples, the first reflector 415 may form one aperture (e.g., eitherthe input aperture 430 or the output aperture 435) and the secondreflector 420 may form the other aperture (e.g., either the inputaperture 430 or the output aperture 435).

The optical device 401 may be configured as a wavelength multiplexer. Insome cases, the optical device 401 may be configured as a wavelengthdemultiplexer. In such cases, the inputs and outputs of the opticaldevice 401 may be reversed. An input fiber 450 may be positioned a firstdistance away from the input aperture 430 and may be configured totransmit one or more optical signals into the optical device 401. Theinput fiber 450 may be an example of an optical communications link 105or one or more optical communication links 130 described with referenceto FIG. 1A. An output fiber 455 may be positioned a second distance awayfrom the output aperture 435 of the optical device 401 and may beconfigured to receive one or more optical signals output from theoptical device 401. The output fiber 455 may be an example of an opticalcommunications link 105 described with reference to FIG. 1A. In somecases, the input fiber 450, the output fiber 455, or any combinationthereof, may be examples of fiber arrays with a plurality of opticalfibers. In some cases, the first distance may be the same size as thesecond distance. In some cases, the first distance may be a sizedifferent than the size of the second distance. In some cases,additional spacers, additional OCAs, or a combination thereof may bepositioned between the input fiber 450 and the optical device 401. Insome cases, additional spacers, additional OCAs, or a combinationthereof may be positioned between the output fiber 455 and the opticaldevice 401. Such additional spacers or additional OCAs may be configuredto reduce back reflection, protect the metamaterials, or provide thespacings between fibers and the optical device, or any combinationthereof.

In examples where the optical device 401 is configured as a wavelengthmultiplexer, the input fiber 450 may be an example of a fiber array andmay transmit two or more optical signals having different wavelengthsinto the optical device 401. The two or more optical signals may bereflected through the optical device 401 by the first reflector 415 andthe second reflector 420 and may pass through the different stages 410of metamaterials (and other components) of the optical device 401. Ateach stage 410, the phase profiles of the two or more optical signalsmay be shifted or altered. The optical device 401, through the differentstages 410, may combine the two or more optical signals into a singleoptical signal having the different wavelengths. The output fiber 455may be an example of a single-output fiber and may be configured toreceive the optical signal that has been multiplexed to include themultiple wavelengths. In some cases, the input fiber 450 may include oneor more SMFs and the one or more input signals may be single-mode inputsignals. In other examples, the input fiber 450 may include one or moreFMFs or MMFs and at least one input signal may be a multi-mode signal.Additionally or alternatively, the output fiber 455 may include one ormore SMFs and the one or more output signals may be single-mode outputsignals. In other examples, the output fiber 455 may include one or moreFMFs or MMFs and at least one output signal may be a multi-mode signal.

In examples where the optical device 401 is configured as a wavelengthdemultiplexer, the input fiber 450 may be an example of a single fiberand may transmit one optical signal that has different wavelengths intothe optical device 401. The optical signal may be reflected through theoptical device 401 by the first reflector 415 and the second reflector420 and may pass through the different stages 410 of metamaterials (andother components) of the optical device 401. At each stage 410, thephase profile of the optical signal may be shifted or altered. Theoptical device 401, through the different stages 410, may separate theoptical signal into two or more different optical signals having thedifferent wavelengths. The output fiber 455 may be an example of a fiberarray and may be configured to receive the two or more optical signalsthat has been demultiplexed from the original optical signal.

In some cases, the optical device 401 may be used for WDM application.The optical device 401 may coherently adjust wavelengths of light intothe same optical signal or out of the same optical signal into differentoptical signals. The light in the first stage of metamaterials maypropagate in many directions, and may interfere with each other whiletraveling to or on the second stage of metamaterials. The second stageof metamaterials may propagate light in many directions, which light mayinterfere with each other while traveling to or on the third stage ofmetamaterials.

FIG. 4B illustrates an example of an optical device 402 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical device 402 may use optically-transmissivemetamaterial structures, an optically-transmissive substrate, andreflectors in a folded design to perform wavelength multiplexing orwavelength demultiplexing techniques. The optical device 402 may be anexample of the optical devices 202 and 401 described with reference toFIGS. 2B and 4A. The optical device 402 may be similarly embodied as theoptical device 401 and similarly numbered and named elements may beembodied similarly.

The optical device 402 may include a few features that are differentthan the optical device 401 described with reference to FIG. 4A. Forexample, the input aperture 430 may be formed in the second reflector420 by the one or more sidewalls 440, and the output aperture 435continues to be formed in the first reflector 415 by the one or moresidewalls 445. An input optical signal may pass through the first stage410-a of metamaterials before passing through the substrate 405. In suchcases, the input aperture 430 may be positioned in the second reflector420 that is positioned near the stages 410 of metamaterials. Inaddition, the input signal may be transmitted at an approximatelyorthogonal angle relative to a plane of the input aperture 430 or theplane of the first stage 410-a of metamaterials. The first stage 410-aof metamaterials may be configured to alter the direction of travel ofthe optical signal. The last stage 410-N of metamaterials may be alsoconfigured to alter the direction of travel of the optical signal. Insome cases, the second reflector 420, the last stage 410-N ofmetamaterials, or any combination thereof may be configured to alter thedirection of travel of the optical signal. In some cases, the firststage 410-a of metamaterials may be an example of a transmissive stageof metamaterials and the subsequent stages 410 of metamaterials may beexamples of reflective stages of metamaterials.

FIG. 4C illustrates an example of an optical device 403 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical device 403 may use optically-transmissivemetamaterial structures, an optically-transmissive substrate, andreflectors in a folded design to perform wavelength multiplexing orwavelength demultiplexing techniques. The optical device 403 may be anexample of the optical devices 202, 401, and 402 described withreference to FIGS. 2B and 4A-4B. The optical device 403 may be similarlyembodied as the optical device 401 and similarly numbered and namedelements may be embodied similarly.

The optical device 403 may include a few features that are differentthan the optical device 401 described with reference to FIG. 4A. Theinput aperture 430 may be formed in the second reflector 420 by the oneor more sidewalls 440, and the output aperture 435 continues to beformed in the first reflector 415 by the one or more sidewalls 445. Aninput optical signal may pass through the cladding 425 (without anystage of metamaterials) before passing through the substrate 405. Insuch cases, the input aperture 430 may be positioned in the secondreflector 420 positioned near the stages 410 of metamaterials. The inputsignal may be configured to be transmitted into the optical device 403at an angle that is non-orthogonal relative to a plane defined by theinput aperture 430, a plane defined by the reflectors 415, 420, a planedefined by the cladding 425, a plane defined by the stages 410 ofmetamaterials, or a plane defined by the substrate 405, or anycombination thereof. The non-orthogonal angle may be configured to causethe optical signal to reflect between the reflectors 415, 420 along anoptical path to the successive stages 410 of metamaterials. The laststage 410-N of metamaterials may be also configured to alter thedirection of travel of the optical signal. In some cases, the secondreflector 420, the last stage 410-N of metamaterials, or any combinationthereof may be configured to alter the direction of travel of theoptical signal.

FIG. 4D illustrates an example of an optical device 406 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical device 406 may use optically-transmissivemetamaterial structures, an optically-transmissive substrate, andreflectors in a folded design to perform wavelength multiplexing orwavelength demultiplexing techniques. The optical device 406 may be anexample of the optical devices 202, 401, 402, and 403 described withreference to FIGS. 2B and 4A-4C. The optical device 406 may be similarlyembodied as the optical device 401 and similarly numbered and namedelements may be embodied similarly.

The optical device 406 may include a few features that are differentthan the optical device 401 described with reference to FIG. 4A. Forinstance, the stages 410 of metamaterials may be positioned adjacent tothe first reflector 415, rather than second reflector 420 (as comparedwith the optical device 401). The input aperture 430 may be formed inthe second reflector 420 by the one or more sidewalls 440, and theoutput aperture 435 continues to be formed in the first reflector 415 bythe one or more sidewalls 445. The input aperture 430 is positioned inthe second reflector 420 that is positioned on the opposite side of thesubstrate 405 from the stages 410 of metamaterials. The input signal maybe transmitted into the optical device 403 at an angle that isnon-orthogonal relative to a plane defined by the input aperture 430, aplane defined by the reflectors 415, 420, a plane defined by thecladding 425, a plane defined by the stages 410 of metamaterials, or aplane defined by the substrate 405, or any combination thereof. Thenon-orthogonal angle may be configured to cause the optical signal toreflect between the reflectors 415, 420 along an optical path to thesuccessive stages 410 of metamaterials. The output signal may be outputthrough the output aperture 435 at an angle that is non-orthogonalrelative to a plane defined by the input aperture 430, a plane definedby the reflectors 415, 420, a plane defined by the cladding 425, a planedefined by the stages 410 of metamaterials, or a plane defined by thesubstrate 405, or any combination thereof.

FIG. 4E illustrates an example of an optical device 407 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The optical device 407 may use optically-transmissivemetamaterial structures, an optically-transmissive substrate, andreflectors in a folded design to perform wavelength multiplexing orwavelength demultiplexing techniques. The optical device 407 may be anexample of the optical devices 202, 401, 402, 403, and 406 describedwith reference to FIGS. 2B and 4A-4D. The optical device 407 may besimilarly embodied as the optical device 401 and similarly numbered andnamed elements may be embodied similarly.

The optical device 407 may include a few features that are differentthan the optical device 401 described with reference to FIG. 4A. Theoptical device 407 may include stages 410 of metamaterials positionedadjacent near both the first reflector 415 and the second reflector 420.For example, the first stage 410-a of metamaterials may be positionedadjacent to the first reflector 415 and the second stage 410-b ofmetamaterials may be positioned adjacent to the second reflector 420.The optical device 407 also includes a second cladding 425-a to protectthe stages 410 of metamaterials positioned near the first reflector 415.In optical device 407, stages 410 of metamaterials may be positioned atevery reflection point of the optical path in the optical device 407. Insome examples, at least one reflection point in the optical device 407may not be associated with a stage of metamaterials. In such examples,the optical signal may be reflected at least once by one of thereflectors 415 or 420 without passing through a stage 410 ofmetamaterials.

The input aperture 430 may be formed in the second reflector 420 by theone or more sidewalls 440, and the output aperture 435 continues to beformed in the first reflector 415 by the one or more sidewalls 445. Aninput optical signal may pass through the cladding 425 (without anystage of metamaterials) before passing through the substrate 405. Insuch cases, the input aperture 430 may be positioned in the secondreflector 420 that is positioned near the stages 410 of metamaterials.In some examples, a stage 410 of metamaterials may be positioned in thecladding 425 just below the input aperture 430. Additionally oralternatively, in some examples, a stage of metamaterials may bepositioned in the cladding 425-a just above the output aperture 435. Thefirst stage 410-a of metamaterials and the last stage 410-N ofmetamaterials may be also configured to alter the direction of travel ofthe optical signal. In some cases, the first reflector 415, the firststage 410-a of metamaterials, or any combination thereof may beconfigured to alter the direction of travel of the optical signal. Insome cases, the second reflector 420, the last stage 410-N ofmetamaterials, or any combination thereof may be configured to alter thedirection of travel of the optical signal.

In some examples, the optical devices 401, 402, 403, 406, or 407 may beconfigured as examples of resonant folded designs. In such designs, thegeneral structure of the optical devices is similar to the designs forfolded designs. A difference between a folded design and a resonantfolded design may include the design of the phase profiles of the stagesof the metamaterials. For example, in both stacked designs and foldeddesigns, there may be a fixed number of times the light interacts withthe stages of metamaterials. In a resonant folded design, however, it ispossible for the light to interact with the stages of metamaterials arelatively large number of times (e.g., on the order of hundreds orthousands of times), or in essence an indefinite or infinite number oftimes. In a resonant folded design, a top surface of the substrate 405and a bottom surface of the substrate 405 may form a Fabry-Perot cavity,with stages 410 of metamaterials positioned near such surfaces with oneor more specific phase profiles. In such examples, a single stage 410 ofmetamaterials can interact more strongly with the light as compared withdesigns where a single stage of metamaterials interacts with the lightonce.

To find the appropriate phase profile for the resonant structure, theelectric field inside the metamaterials may be solved under a stationarycondition, using an iterative solver (such as Conjugate Gradient (CG),Conjugate Gradient Squared (CGS), Generalized Minimal RESidual iteration(GMRES), Loose GMRES (LGMRES), etc.). An adjoint analysis may beimplemented, similar to those described above, to calculate the derivateof the figure of merit with respect to the phase profile, and anonlinear enhancement may be used to converge the design.

FIGS. 5A-5F illustrate an example of a method for manufacturing anoptical device that supports a wavelength multiplexer or demultiplexerthat uses metamaterials for optical fiber communications in accordancewith examples as disclosed herein. Each of FIGS. 5A-5F illustrate aperspective view of a cut-away portion of a larger optical device. Thecut-away portion in each figure has been limited to illustrate howvarious aspects of the optical device are formed, but additionalstructure and functionality supporting a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communicationsare contemplated. The operations described herein may be used to formany of the optical devices described with reference to FIGS. 2A-4E. Themethod may be a top-down approach to forming an optical device.

FIG. 5A illustrates an example of a first operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thefirst operation may not be the first step in the manufacturing processfor the optical device, but it is the first operation described in FIGS.5A-5F. FIG. 5A illustrates an optical device 501 that includes asubstrate 510 and a layer of metamaterial 515. The optical device 501 isa device as it occurs after the first operation in the manufacturingprocess is complete.

The first operation may include forming the substrate 510 (e.g., by oneor more deposition steps and/or one or more etching steps). Thesubstrate 510 may be an example of the substrates 205, 305, and 405described with reference to FIGS. 2A-4E. In some cases, the substrate510 may be formed of glass or fused silica. In some examples, thesubstrate 510 may be grown rather than deposited. The terms depositedand grown may be used interchangeably herein.

Also, as part of the first operation, the layer of metamaterial 515 maybe deposited on the substrate 510. In some cases, the layer ofmetamaterial 515 may be an example of metamaterials that are used toform the metamaterial structures in the finished optical device. Thelayer of metamaterials 515 may be an example of the metamaterialstructures or stages of metamaterials described with reference to FIGS.2A-4E.

FIG. 5B illustrates an example of a second operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thesecond operation occurs after the first operation described withreference to FIG. 5A. In some cases, other steps or operations may occurbetween the first operation and the second operation. FIG. 5Billustrates an optical device 502 that includes the substrate 510, thelayer of metamaterial 515, and the resist layer 520. The optical device502 is a device as it occurs after the second operation in themanufacturing process is complete.

In the second operation, a resist layer 520 is deposited or coated onthe layer of metamaterial 515. In some cases, the resist layer 520 maybe an example of a hard mask material or sacrificial layer, or anycombination thereof.

FIG. 5C illustrates an example of a third operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thethird operation occurs after the second operation described withreference to FIG. 5B. In some cases, other steps or operations may occurbetween the second operation and the third operation. FIG. 5Cillustrates an optical device 503 that includes the substrate 510, thelayer of metamaterial 515, and a plurality of hardmasks 525 formed fromthe resist layer 520. The optical device 503 is a device as it occursafter the third operation in the manufacturing process is complete.

In the third operation, portions of the resist layer 520 are removed toform the plurality of hardmasks 525. Each hardmask 525 of the pluralityof hardmasks include one or more parameters (e.g., cross-sectionalprofile, cross-sectional area, or height) that are configured to controlthe parameters of the metamaterial structures that result from theplurality of hardmasks 525. The plurality of hardmasks 525 may be formedusing one or more etching processes, e-beam lithography,photo-lithography, nanoimprint, or any combination thereof.

FIG. 5D illustrates an example of a fourth operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thefourth operation occurs after the third operation described withreference to FIG. 5C. In some cases, other steps or operations may occurbetween the third operation and the fourth operation. FIG. 5Dillustrates an optical device 504 that includes the substrate 510 and aplurality of metamaterial structures 530 formed from the layer ofmetamaterial 515 and were formed based on the parameters of theplurality of hardmasks 525. The optical device 504 is a device as itoccurs after the fourth operation in the manufacturing process iscomplete.

In the fourth operation, portions of the layer of metamaterials 515 andthe plurality of hardmasks 525 are removed to form the plurality ofmetamaterial structures 530. In some cases, a pattern of the resistlayer may be etched. Each metamaterial structure 530 of the plurality ofmetamaterial structures include one or more parameters (e.g.,cross-sectional profile, cross-sectional area, or height) that areconfigured based on the parameters of the hardmasks initially positionedabove the metamaterial structure. The plurality of metamaterialstructures 530 may be formed using one or more etching processes, e-beamlithography, photo-lithography, nanoimprint, or any combination thereof.In some cases, a single process from the processes listed above may beused as part of the fourth operation. In some cases, two or moreprocesses from the processes listed above may be used as part of thefourth operation.

FIG. 5E illustrates an example of a fifth operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thefifth operation occurs after the fourth operation described withreference to FIG. 5D. In some cases, other steps or operations may occurbetween the fourth operation and the fifth operation. FIG. 5Eillustrates an optical device 505 that includes the substrate 510, aplurality of metamaterial structures 530, and cladding 535. The opticaldevice 505 is a device as it occurs after the fifth operation in themanufacturing process is complete.

In the fifth operation, cladding 535 is deposited on the substrate 510and the plurality of metamaterial structures 530. The cladding 535 maybe an example of the cladding 215 or the cladding 425 described withreference to FIGS. 2A and 4A-4E. The cladding 535 may be configured toprotect the metamaterial structures 530 from damage, mitigate losses ofoptical signals interacting with the metamaterial structures, or anycombination thereof.

FIG. 5F illustrates an example of a sixth operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thesixth operation occurs after the fifth operation described withreference to FIG. 5D. In some cases, other steps or operations may occurbetween the fifth operation and the sixth operation. FIG. 5F illustratesan optical device 506 that includes the substrate 510, a plurality ofmetamaterial structures 530, cladding 535, and a reflector 540. Theoptical device 506 is a device as it occurs after the sixth operation inthe manufacturing process is complete.

In the sixth operation, a material is deposited to form the reflector540. In some cases, the material is a reflective material (e.g., a metalsuch as gold). In some cases, the material is coated with a reflectivematerial (e.g., a metal such as gold) to form the reflector 540. Thereflector 540 may be formed to be positioned in proximity to or incontact with the cladding 535. In some cases, the cladding 535 ispositioned between the metamaterial structures 530 and the reflector540. The reflector 540 may be an example of the reflectors 220, 415, and420 described with reference to FIGS. 2B and 4A-4E. In some cases, theoptical device 506 may represent a portion of a completed memory devicedescribed with reference to FIGS. 2A-4E.

In the top-down approach to manufacturing the optical device, a materialused for the metamaterial structures is put on the substrate 510, asdescribed in FIG. 5A, by processes such as wafer bonding and/or filmdeposition processes such as plasma enhanced chemical vapor deposition(PECVD), low pressure chemical vapor deposition (LPCVD), atomic layerdeposition (ALD), thermal evaporation, e-beam evaporation, sputtering,and so on. The techniques for patterning the structure (e.g., FIGS. 5Band 5C) can be lithography methods, such as e-beam lithography,photolithography, nanoimprint lithography, or any combination thereof.Other techniques such as self-assembly may also be utilized to patternthe device. Depending on the techniques and materials chosen for thedevice, different resist and etching techniques can be employed totransfer the pattern to the metamaterial layer as shown in FIG. 5D(e.g., the techniques can be dry etching techniques, such as reactiveion etching, inductively coupled plasma etching, or ion milling, or anycombination thereof). In some cases, another layer of other materialscan be added on top of the thin film layer (e.g., the layer ofmetamaterial 515) to act as a hard mask in the etching process, insteadof using the resist as the etching mask. Depending on the design, acladding layer can be added to protect or support the structure, whichmay be added using coating techniques (such as spin coating) ordeposition techniques described herein (e.g., as shown in FIG. 5E). Thereflector (e.g., metal) layer can be added on top of the cladding layerusing deposition techniques described herein (e.g., as shown in FIG.5F).

FIGS. 6A-6F illustrate an example of a method for manufacturing anoptical device that supports a wavelength multiplexer or demultiplexerthat uses metamaterials for optical fiber communications in accordancewith examples as disclosed herein. Each of FIGS. 6A-6F illustrate aperspective view of a cut-away portion of a larger optical device. Thecut-away portion in each figure has been limited to illustrate howvarious aspects of the optical device are formed, but additionalstructure and functionality supporting a wavelength multiplexer ordemultiplexer that uses metamaterials for optical fiber communicationsare contemplated. The operations described herein may be used to formany of the optical devices described with reference to FIGS. 2A-4E. Themethod may be a bottom-up approach to forming an optical device.

FIG. 6A illustrates an example of a first operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thefirst operation may not be the first step in the manufacturing processfor the optical device, but it is the first operation described in FIGS.6A-6F. FIG. 6A illustrates an optical device 601 that includes asubstrate 610 and a resist layer 615. The optical device 601 is a deviceas it occurs after the first operation in the manufacturing process iscomplete.

The first operation may include forming the substrate 610 (e.g., by oneor more deposition steps and/or one or more etching steps). Thesubstrate 610 may be an example of the substrates 205, 305, and 405described with reference to FIGS. 2A-4E. In some examples, the substrate610 may be grown rather than deposited (e.g., using a Czochralskiprocess). The terms deposited and grown may be used interchangeablyherein.

Also, as part of the first operation, a resist layer 615 may bedeposited or coated on the substrate 610. In some cases, the resistlayer 615 may be an example of a hard mask material or sacrificiallayer, or any combination thereof.

FIG. 6B illustrates an example of a second operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thesecond operation occurs after the first operation described withreference to FIG. 6A. In some cases, other steps or operations may occurbetween the first operation and the second operation. FIG. 6Billustrates an optical device 602 that includes the substrate 610, theresist layer 615, and a plurality of cavities 620 formed in the resistlayer 615. The optical device 602 is a device as it occurs after thesecond operation in the manufacturing process is complete.

In the second operation, portions of the resist layer 615 are removed toform the plurality of cavities 620. In some cases, a pattern of theresist layer 615 may be etched. Each cavity 620 of the plurality ofcavities may include one or more parameters (e.g., cross-sectionalprofile, cross-sectional area, or height) that are configured to controlthe parameters of the metamaterial structures that result from theplurality of cavities 620. The plurality of cavities 620 may be formedusing one or more etching processes, e-beam lithography,photo-lithography, nanoimprint, or any combination thereof.

FIG. 6C illustrates an example of a third operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thethird operation occurs after the second operation described withreference to FIG. 6B. In some cases, other steps or operations may occurbetween the second operation and the third operation. FIG. 6Cillustrates an optical device 603 that includes the substrate 610, theresist layer 615, and the layer of metamaterial 625. The optical device603 is a device as it occurs after the third operation in themanufacturing process is complete.

In the third operation, the layer of metamaterial 625 may be depositedon the resist layer 615 and in the plurality of cavities 620 formed inthe resist layer 615. In some cases, the layer of metamaterial 625 maybe an example of metamaterials that are used to form the metamaterialstructures in the finished optical device. The layer of metamaterials625 may be an example of the metamaterial structures or stages ofmetamaterials described with reference to FIGS. 2A-4E. In some cases,the layer of metamaterial 625 may also include a plurality of cavitiesafter being deposited. In such cases, the thickness of the depositedfilm may be uniform across the device. In such cases, material of thelayer of metamaterial 625 that fills the plurality of cavities 620 mayleave a similar cavity above it in the layer of metamaterial 625.

FIG. 6D illustrates an example of a fourth operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thefourth operation occurs after the third operation described withreference to FIG. 6C. In some cases, other steps or operations may occurbetween the third operation and the fourth operation. FIG. 6Dillustrates an optical device 604 that includes the substrate 610 and aplurality of metamaterial structures 630 formed from the layer ofmetamaterial 625 and were formed based on the parameters of theplurality of cavities 620. The optical device 604 is a device as itoccurs after the fourth operation in the manufacturing process iscomplete.

In the fourth operation, portions of the layer of metamaterials 625 andthe remaining portions of the resist layer 615 are removed to form (orexpose) the plurality of metamaterial structures 630. Each metamaterialstructure 630 of the plurality of metamaterial structures include one ormore parameters (e.g., cross-sectional profile, cross-sectional area, orheight) that are configured based on the parameters of the cavities intowhich the layer of metamaterial 625 was deposited. In some cases, one ormore chemicals may be applied to the optical device 604 to remove theremaining resist layer and the metamaterials that are on top of theremaining resist layer. In some cases, this procedure may be referred toas lift-off. The plurality of metamaterial structures 630 may be formedusing one or more etching processes, e-beam lithography,photo-lithography, nanoimprint, or a lift-off process, or anycombination thereof. In some cases, a single process from the processeslisted above may be used as part of the fourth operation. In some cases,two or more processes from the processes listed above may be used aspart of the fourth operation.

FIG. 6E illustrates an example of a fifth operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thefifth operation occurs after the fourth operation described withreference to FIG. 6D. In some cases, other steps or operations may occurbetween the fourth operation and the fifth operation. FIG. 6Eillustrates an optical device 605 that includes the substrate 610, aplurality of metamaterial structures 630, and cladding 635. The opticaldevice 605 is a device as it occurs after the fifth operation in themanufacturing process is complete.

In the fifth operation, cladding 635 is deposited on the substrate 610and the plurality of metamaterial structures 630. The cladding 635 maybe an example of the cladding 215 or the cladding 425 described withreference to FIGS. 2A and 4A-4E. The cladding 635 may be configured toprotect the metamaterial structures 630 from damage, mitigate losses ofoptical signals interacting with the metamaterial structures, or anycombination thereof.

FIG. 6F illustrates an example of a sixth operation of a method formanufacturing an optical device that supports a wavelength multiplexeror demultiplexer that uses metamaterials for optical fibercommunications in accordance with examples as disclosed herein. Thesixth operation occurs after the fifth operation described withreference to FIG. 6E. In some cases, other steps or operations may occurbetween the fifth operation and the sixth operation. FIG. 6F illustratesan optical device 606 that includes the substrate 610, a plurality ofmetamaterial structures 630, cladding 635, and a reflector 640. Theoptical device 606 is a device as it occurs after the sixth operation inthe manufacturing process is complete.

In the sixth operation, a material is deposited to form the reflector640. In some cases, the material is a reflective material (e.g., a metalsuch as gold). In some cases, the material is coated with a reflectivematerial (e.g., a metal such as gold) to form the reflector 640. Thereflector 640 may be formed to be positioned in proximity to or incontact with the cladding 635. In some cases, the cladding 635 ispositioned between the metamaterial structures 630 and the reflector640. The reflector 640 may be an example of the reflectors 220, 415, and420 described with reference to FIGS. 2B and 4A-4E. In some cases, theoptical device 606 may represent a portion of a completed memory devicedescribed with reference to FIGS. 2A-4E.

In the bottom-up approach, the inverse pattern of the desired structurecan be first created using lithography techniques, similar to thetop-down approach (e.g., see FIGS. 6A and 6B). A thin film layer maythen be grown on top of the patterned resist layer 615, filling theholes (e.g., see FIG. 6C). After a lift-off process (e.g., see FIG. 6D),the resist layer 615 as well as the thin film on top the resist can beremoved, and the pattern is transferred to the thin film layer to becomethe metamaterial structures. Depending on the design, a cladding layercan be added to protect or support the structure, using coatingtechniques (such as spin coating) or deposition techniques describedherein (e.g., as shown in FIG. 6E). The reflector (e.g., metal) layercan be added on top of the cladding layer using deposition techniquesdescribed herein (e.g., as shown in FIG. 6F).

FIG. 7 shows a flowchart illustrating a method 700 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The operations of method 700 may be implemented by amanufacturing system or one or more controllers associated with amanufacturing system. In some examples, one or more controllers mayexecute a set of instructions to control one or more functional elementsof the manufacturing system to perform the described functions.Additionally or alternatively, one or more controllers may performaspects of the described functions using special-purpose hardware.

At 705, the method 700 may include growing a substrate that is opticallytransmissive. The operations of 705 may be performed according to themethods described herein.

At 710, the method 700 may include depositing a layer of metamaterial onthe substrate. The operations of 710 may be performed according to themethods described herein.

At 715, the method 700 may include depositing a resist layer on thelayer of metamaterial. The operations of 715 may be performed accordingto the methods described herein.

At 720, the method 700 may include etching a pattern of the resist layerto form a set of hardmasks. In some cases, a portion of the resist layermay be etched. The operations of 720 may be performed according to themethods described herein.

At 725, the method 700 may include etching the set of hardmasks andexposed portions of the layer of metamaterial to form a set ofmetamaterial structures based on etching the portion of the resistlayer, where the set of metamaterial structures are configured to shiftphase profiles of a first optical signal having a first wavelength and asecond optical signal having a second wavelength to multiplex the firstoptical signal and the second optical signal into a third optical signalhaving the first wavelength and the second wavelength. In some cases,the set of metamaterial structures may be formed by etching the layer ofmetamaterial while using the resist as one or more hardmasks during theetching process. The operations of 725 may be performed according to themethods described herein.

In some examples, an apparatus as described herein may perform a methodor methods, such as the method 700. The apparatus may include features,means, or instructions (e.g., a non-transitory computer-readable mediumstoring instructions executable by a processor) for growing a substratethat is optically transmissive, depositing a layer of metamaterial onthe substrate, depositing a resist layer on the layer of metamaterial,etching a portion of the resist layer to form a set of hardmasks, andetching the set of hardmasks and exposed portions of the layer ofmetamaterial to form a set of metamaterial structures based on etchingthe portion of the resist layer. The set of metamaterial structures maybe configured to shift phase profiles of a first optical signal having afirst wavelength and a second optical signal having a second wavelengthto multiplex the first optical signal and the second optical signal intoa third optical signal having the first wavelength and the secondwavelength.

Some examples of the method 700 and the apparatus described herein mayfurther include operations, features, means, or instructions fordepositing a reflective material to form a reflector at one end of theset of metamaterial structures based on etching the set of hardmasks andthe exposed portions of the layer of metamaterial. Some examples of themethod 700 and the apparatus described herein may further includeoperations, features, means, or instructions for depositing cladding onthe set of metamaterial structures and on exposed portions of thesubstrate based on etching the set of hardmasks and the exposed portionsof the layer of metamaterial, where depositing the reflective materialmay be based on depositing the cladding. In some examples of the method700 and the apparatus described herein, the reflective material may bedeposited on the cladding that may be positioned between the set ofmetamaterial structures and the reflective material.

In some examples of the method 700 and the apparatus described herein,each metamaterial structure of the set of metamaterial structures mayhave one or more parameters that includes a height of the metamaterialstructure, a cross-sectional profile of the metamaterial structure, adiameter of the metamaterial structure, a dielectric property of themetamaterial structure, or any combination thereof. In some examples ofthe method 700 and the apparatus described herein, at least some of theone or more parameters of each metamaterial structure may be based on asecond cross-sectional profile of an associated hardmask.

FIG. 8 shows a flowchart illustrating a method 800 that supports awavelength multiplexer or demultiplexer that uses metamaterials foroptical fiber communications in accordance with examples as disclosedherein. The operations of method 800 may be implemented by amanufacturing system or one or more controllers associated with amanufacturing system. In some examples, one or more controllers mayexecute a set of instructions to control one or more functional elementsof the manufacturing system to perform the described functions.Additionally or alternatively, one or more controllers may performaspects of the described functions using special-purpose hardware.

At 805, the method 800 may include depositing a substrate that isoptically transmissive. The operations of 805 may be performed accordingto the methods described herein.

At 810, the method 800 may include depositing a resist layer on thesubstrate. The operations of 810 may be performed according to themethods described herein.

At 815, the method 800 may include etching a pattern of the resist layerto form a set of cavities in the resist layer. In some cases, a portionof the resist layer may be etched. The operations of 815 may beperformed according to the methods described herein.

At 820, the method 800 may include depositing a layer of metamaterial onthe resist layer that forms the set of cavities, the layer ofmetamaterial filling at least some of the set of cavities formed in theresist layer. The operations of 820 may be performed according to themethods described herein.

At 825, the method 800 may include removing the layer of metamaterialand the resist layer to form a set of metamaterial structures based ondepositing the layer of metamaterial on the resist layer, where the setof metamaterial structures are configured to shift phase profiles of afirst optical signal having a first wavelength and a second opticalsignal having a second wavelength to multiplex the first optical signaland the second optical signal into a third optical signal having thefirst wavelength and the second wavelength. In some cases, one or morechemicals may be applied to the structure to remove the remaining resistlayer and the metamaterials that are on top of the remaining resistlayer. In some cases, this procedure may be referred to as lift-off. Theoperations of 825 may be performed according to the methods describedherein.

In some examples, an apparatus as described herein may perform a methodor methods, such as the method 800. The apparatus may include features,means, or instructions (e.g., a non-transitory computer-readable mediumstoring instructions executable by a processor) for depositing asubstrate that is optically transmissive, depositing a resist layer onthe substrate, etching a portion of the resist layer to form a set ofcavities in the resist layer, depositing a layer of metamaterial on theresist layer that forms the set of cavities, the layer of metamaterialfilling at least some of the set of cavities formed in the resist layer,and etching the layer of metamaterial and the resist layer to form a setof metamaterial structures based on depositing the layer of metamaterialon the resist layer. The set of metamaterial structures can beconfigured to shift phase profiles of a first optical signal having afirst wavelength and a second optical signal having a second wavelengthto multiplex the first optical signal and the second optical signal intoa third optical signal having the first wavelength and the secondwavelength.

Some examples of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions fordepositing a reflective material to form a reflector at one end of theset of metamaterial structures based on etching the layer ofmetamaterial and the resist layer. Some examples of the method 800 andthe apparatus described herein may further include operations, features,means, or instructions for depositing cladding on the set ofmetamaterial structures and on exposed portions of the substrate basedon etching the layer of metamaterial and the resist layer, wheredepositing the reflective material may be based on depositing thecladding. In some examples of the method 800 and the apparatus describedherein, the reflective material may be deposited on the cladding thatmay be positioned between the set of metamaterial structures and thereflective material.

In some examples of the method 800 and the apparatus described herein,each metamaterial structure of the set of metamaterial structures mayhave one or more parameters of the metamaterial structure includes aheight of the metamaterial structure, a cross-sectional profile of themetamaterial structure, a diameter of the metamaterial structure, adielectric property of the metamaterial structure, or any combinationthereof. In some examples of the method 800 and the apparatus describedherein, at least some of the one or more parameters of each metamaterialstructure may be based on a second cross-sectional profile of anassociated cavity in the resist layer.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Furthermore, portions from two or more of the methods may be combined.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof. Some drawings may illustrate signals as a single signal;however, it will be understood by a person of ordinary skill in the artthat the signal may represent a bus of signals, where the bus may have avariety of bit widths.

The terms “electronic communication,” “conductive contact,” “connected,”and “coupled” may refer to a relationship between components thatsupports the flow of signals between the components. Components areconsidered in electronic communication with (or in conductive contactwith or connected with or coupled with) one another if there is anyconductive path between the components that can, at any time, supportthe flow of signals between the components. At any given time, theconductive path between components that are in electronic communicationwith each other (or in conductive contact with or connected with orcoupled with) may be an open circuit or a closed circuit based on theoperation of the device that includes the connected components. Theconductive path between connected components may be a direct conductivepath between the components or the conductive path between connectedcomponents may be an indirect conductive path that may includeintermediate components, such as switches, transistors, or othercomponents. In some examples, the flow of signals between the connectedcomponents may be interrupted for a time, for example, using one or moreintermediate components such as switches or transistors.

The devices discussed herein, including an optical device, may be formedon a semiconductor substrate, such as silicon, germanium,silicon-germanium alloy, gallium arsenide, gallium nitride, etc. In someexamples, the substrate is a semiconductor wafer. In other examples, thesubstrate may be a silicon-on-insulator (SOI) substrate, such assilicon-on-glass (SOG) or silicon-on-sapphire (SOP), or epitaxial layersof semiconductor materials on another substrate. The conductivity of thesubstrate, or sub-regions of the substrate, may be controlled throughdoping using various chemical species including, but not limited to,phosphorous, boron, or arsenic. Doping may be performed during theinitial formation or growth of the substrate, by ion-implantation, or byany other doping means.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details toproviding an understanding of the described techniques. Thesetechniques, however, may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form to avoid obscuring the concepts of the described examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated-circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any processor, controller,microcontroller, or state machine. A processor may also be implementedas a combination of computing devices (e.g., a combination of a digitalsignal processor (DSP) and a microprocessor, multiple microprocessors,one or more microprocessors in conjunction with a DSP core, or any othersuch configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, asused herein, the phrase “based on” shall not be construed as a referenceto a closed set of conditions. For example, an exemplary step that isdescribed as “based on condition A” may be based on both a condition Aand a condition B without departing from the scope of the presentdisclosure. In other words, as used herein, the phrase “based on” shallbe construed in the same manner as the phrase “based at least in parton.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise random-access memory (RAM), read-only memory (ROM),electrically erasable programmable read-only memory (EEPROM), compactdisk (CD) ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other non-transitory medium thatcan be used to carry or store desired program code means in the form ofinstructions or data structures and that can be accessed by ageneral-purpose or special-purpose computer, or a general-purpose orspecial-purpose processor. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwaveare included in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other variations without departing fromthe scope of the disclosure. Thus, the disclosure is not limited to theexamples and designs described herein, but is to be accorded thebroadest scope consistent with the principles and novel featuresdisclosed herein.

What is claimed is:
 1. An apparatus, comprising: a first substrate thatis optically transmissive; a first stage of metamaterials in contactwith the first substrate; a second stage of metamaterials in contactwith the first substrate; and a reflector positioned opposite the firstsubstrate and configured to reflect an optical signal that passesthrough the first stage of metamaterials to pass through the first stageof metamaterials again, wherein the first stage of metamaterials and thesecond stage of metamaterials are configured to multiplex a firstoptical signal having a first wavelength and a second optical signalhaving a second wavelength into a third optical signal having the firstwavelength and the second wavelength based at least in part on shiftinga first phase profile of the first optical signal and a second phaseprofile of the second optical signal by the first stage of metamaterialsand the second stage of metamaterials.
 2. The apparatus of claim 1,wherein: the first stage of metamaterials is configured to shift thefirst phase profile of the first optical signal and the second phaseprofile of the second optical signal and output a first shifted opticalsignal and a second shifted optical signal; and the second stage ofmetamaterials is configured to shift a third phase profile of the firstshifted optical signal and a fourth phase profile of the second shiftedoptical signal and output the third optical signal that comprises thefirst wavelength and the second wavelength.
 3. The apparatus of claim 1,further comprising: cladding positioned between the first stage ofmetamaterials and the reflector, the cladding having a thicknessconfigured to mitigate losses of optical signals interacting with thefirst stage of metamaterials, or to protect the first stage ofmetamaterials, or a combination thereof.
 4. The apparatus of claim 3,wherein the thickness of the cladding is between 500 nanometers and 2micrometers.
 5. The apparatus of claim 1, further comprising: a firstreflector and a second reflector configured to reflect the first opticalsignal and the second optical signal, the first substrate positionedbetween the first reflector and the second reflector.
 6. The apparatusof claim 5, wherein: the first stage of metamaterials and the secondstage of metamaterials are positioned in proximity to the firstreflector.
 7. The apparatus of claim 5, wherein: the first stage ofmetamaterials is positioned in proximity to the first reflector; and thesecond stage of metamaterials is positioned in proximity to the secondreflector.
 8. The apparatus of claim 5, wherein: the first reflectorforms a first aperture for receiving the first optical signal and thesecond optical signal; and the second reflector forms a second aperturefor outputting the third optical signal.
 9. The apparatus of claim 5,wherein: the first reflector forms a first aperture for receiving thefirst optical signal and the second optical signal and forms a secondaperture for outputting the third optical signal.
 10. The apparatus ofclaim 5, wherein the first substrate, the first reflector, the secondreflector, the first stage of metamaterials, and the second stage ofmaterials form a Fabry-Perot cavity configured to generate one or moreresonant reflections of the first optical signal and the second opticalsignal.
 11. The apparatus of claim 1, wherein the first stage ofmetamaterials comprises: a plurality of metamaterial structures arrangedin a pattern to shift a phase profile of the optical signal based atleast in part on one or more parameters of each metamaterial structureof the plurality of metamaterial structures.
 12. The apparatus of claim11, wherein the one or more parameters of the metamaterial structurecomprises a height of the metamaterial structure, a cross-sectionalprofile of the metamaterial structure, a diameter of the metamaterialstructure, a dielectric property of the metamaterial structure, or acombination thereof, and wherein at least one of the one or moreparameters of the metamaterial structure is different for a firstmetamaterials structure compared to a second metamaterial structure. 13.The apparatus of claim 11, wherein a total phase shifting caused by thefirst stage of metamaterials is based at least in part on a phaseshifting profile of each metamaterial structure and the pattern of theplurality of metamaterial structures.
 14. A method, comprising: growinga substrate that is optically transmissive; depositing a layer ofmetamaterial on the substrate; depositing a resist layer on the layer ofmetamaterial; etching a portion of the resist layer to form a pluralityof hardmasks; and etching the plurality of hardmasks and exposedportions of the layer of metamaterial to form a plurality ofmetamaterial structures based at least in part on etching the portion ofthe resist layer, wherein the plurality of metamaterial structures areconfigured to shift phase profiles of a first optical signal having afirst wavelength and a second optical signal having a second wavelengthto multiplex the first optical signal and the second optical signal intoa third optical signal having the first wavelength and the secondwavelength.
 15. The method of claim 14, further comprising: depositing areflective material to form a reflector at one end of the plurality ofmetamaterial structures based at least in part on etching the pluralityof hardmasks and the exposed portions of the layer of metamaterial. 16.The method of claim 15, further comprising: depositing cladding on theplurality of metamaterial structures and on exposed portions of thesubstrate based at least in part on etching the plurality of hardmasksand the exposed portions of the layer of metamaterial, whereindepositing the reflective material is based at least in part ondepositing the cladding.
 17. The method of claim 16, wherein thereflective material is deposited on the cladding that is positionedbetween the plurality of metamaterial structures and the reflectivematerial.
 18. The method of claim 14, wherein each metamaterialstructure of the plurality of metamaterial structures has one or moreparameters that comprises a height of the metamaterial structure, across-sectional profile of the metamaterial structure, a diameter of themetamaterial structure, a dielectric property of the metamaterialstructure, or a combination thereof.
 19. The method of claim 18, whereinat least some of the one or more parameters of each metamaterialstructure is based at least in part on a second cross-sectional profileof an associated hardmask.
 20. An apparatus, comprising: a substratethat is optically transmissive; a stage of metamaterials in contact withthe substrate; and a reflector positioned opposite the substrate andconfigured to reflect an optical signal that passes through the stage ofmetamaterials to pass through the stage of metamaterials again, whereinthe stage of metamaterials is configured to demultiplex a first opticalsignal having a first wavelength and a second wavelength into a secondoptical signal having the first wavelength and a third optical signalhaving the second wavelength based at least in part on shifting a phaseprofile of the first optical signal by the stage of metamaterials beforeand after the first optical signal reflects from the reflector, thesecond optical signal having a first portion of information conveyed bythe first optical signal and the third optical signal having a secondportion of information conveyed by the first optical signal.
 21. Theapparatus according to claim 1 comprising multiple stages ofmetamaterials, wherein there is no air space separations between saidmultiple stages of metamaterials.
 22. The apparatus of claim 1comprising multiple substrates, and at least one set of first stage ofmetamaterials in contact with each of said substrates.
 23. The apparatusaccording to claim 21 further comprising optically clear adhesives(OCAs) positioned between at least one layer of a substrate at least onestage of metamaterials.
 24. The apparatus according to claim 20, whereinthere is no air space separations between said reflector and said stageof metamaterials.